Women in Mahabharata - Devaki
She is the youngest daughter of Devaka and a cousin of Kamsa through her uncle Ugrasena. She, along with her 6 older sisters, is married to Vasudeva, the son of Aryaka Shoora, the head of a competing Yadava family. In the Ghata-Jataka she is identified as Devagabhha, who gives all her children to a certain attendant called Nandagopa to raise for the time being.
She is also undeniably the mother of Krishna Vaasudeva- in fact the earliest mention that we have found of Krishna by name, in the Chadogya-upanishad, is when he is noted as 'Devaki-putra': "Tadhvaitada Ghora-Aangirasah Krishna-yah Devaki-putra-yah uktvaah uvaacha apipaasa eva sa vabhoova".
It is unclear if her sisters were already married to Vasudeva when her marriage was fixed, or whether they were married to him at Devaki's marriage altar (given conflicting versions exist).
During her marriage, there is a quarrel, where another Yadava cousin Somadatta tries to kidnap her from the altar to marry her himself. Aware of his plan, another cousin, Shini, pulls her away on to his chariot to save her. During this disagreement, Shini kicks Somadatta in the head.
The anger owing to this humiliation, Somadatta infuses in his son Bhoorisrava's head, and it all culminates in Bhoorisrava joining the Kaurava side during the war of Kurukshetra, just to exact revenge on Satyaki, Shini's grandson, and is finally killed by him.
The above story however, gives us a clear view of how Kamsa gained control of Mathura so easily, and so fast. This duel of Shini and Somadatta would have given him the perfect distraction to surround the lot of them with his own army contingents (probably a gift from Jarasandha), and also maybe already arrest his legal-father, Ugrasena.
Bhagavatam then presents a dramatic narrative where Kamsa hears a divine warning proclaiming that Devaki's son will eventually kill him, and then he imprisons both Devaki and Vasudeva after exacting a promise from the latter to get free rein to murder all of Devaki's children.
However, knowing Vasudeva's overall command of the parliament, the above seems like a case of poetic exaggeration, and the couple, after a successful coup led by Kamsa, became politically powerless but were otherwise free to live in their own quarters in Mathura, maybe under supervision or at max, a house arrest.
Then, as per the popular retelling (supported by Bhagavatam), Devaki gives birth to six children, and they are all murdered by Kamsa. Her seventh son is magically transported to Rohini's womb in Gokula, and Krishna is the eighth. Harivamsha and most of the older documents however present a slightly different story.
Here, Balarama is the oldest child of Vasudeva's and Rohini is noted to be pregnant even at the time of Devaki's wedding (after, or slightly before, that drama she flees Mathura and takes up residence with Nanda-gopa, and Balarama is born there, no magic). Bala-charita notes Krishna as the seventh child and Harivamsha notes him as the eighth, but overall, given among Devaki's children he is still seventh.
About the six children too, Dr. Bhaduri, present an interesting analysis. He recounts the backstory given for them in Harivamsha, where the sons of Kalanemi are reborn as Devaki's kids bearing a curse to be killed by their father (that being Kamsa, Kalanemi's Dvapara reincarnation). Together, these danavas are called the 'Shadgarbha'. However, Harivamsha never once clarifies if there are 'six' sons of just one. Hence, Dr. Bhaduri posits that there could have been just one child, named Shadgarbha at birth who was then murdered by Kamsa, making Krishna Devaki's second child, and the name of that one child itself going on to create a ripple effect of new stories in the subsequent puranas. He notes that the narrator of Harivamsha very much uses singular indicators for the child, locking in this possibility. This explanation maintains the 2-3 year age gap between Krishna and Balarama (even though this causes issues with lining them up with the Pandavas) all while maintaining the birth order where Balarama is the oldest.
The night Krishna is born, we know, it was a night of torrential rain. Again subverting Bhagavatham's description of a calm, post-rain lull, in the older text, Krishna is born with the storm fully raging on outside, it rather being an indicator of the tumultuous, transformative life that he is going to lead. Taking advantage of people's fear of this near-calamity, Vasudeva is able to give Kamsa's guards a slip, and he manages to exchange baby-Krishna with the stillborn(??) daughter of Nanda.
Once Devaki gets a hold of the other baby, she tries her level best to shield her as well from Kamsa but is unable to do so, and we also get Yogamaya, the preceptor deity behind the child, warn Kamsa again, post-which overcome with guilt Kamsa backpedals a bit. Her warning can also be explained by the gossip spread by some citizens who might have seen Vasudeva execute his own plans. Here, we see Devaki, though still angry within, be kind to a now-sobbing and apologizing Kamsa and embrace him 'like a mother' [giving a glimpse into how their relationship might have been before this].
Near to his end, Kamsa has called for an emergency midnight sabha of all the Yadava families, invited her and Vasudeva, specifically insulting them and trying to force them to give up Krishna's location (even though it was more of an open secret at that point). This time we see, for the first time in maybe twenty-five years, the former parliament takes a stand, unanimously rebuking Kamsa (mostly confident given their previous talks with Krishna himself and having secured his go-ahead for this). This terrifies the dictator who promptly sends Akroora to immediately bring Krishna and Balarama to Mathura, 'in chains if need be'!
Akroora, without any drama, sits Krishna, Balarama and Nanda down and explains the situation in brief. He then launches into a long-winded expositions about Devaki's mental state given she is probably one of the people that have been most directly and viscerally affected by this turn of events. Akroora also tries to emotionally sway Krishna (wasn't needed, really, but it does set the tone for this character going forward), but telling him, in great detail, how his parents are being insulted just for trying to keep him alive (never mind a parent's inherent duty!).
I personally do not think Devaki would have appreciated being used as a point of manipulation to push her son towards a situation that she has sacrificed so much to have him avoid! Regardless, Krishna had already made up his mind to go, so it didn't matter as much, but he too was annoyed at being micromanaged into doing his duty.
When Krishna finally kills Kamsa, we see Vasudeva (rather than one of the brothers), take charge of the situation. He does it with such finesse, that even Ugrasena and Padmavati have to pull Krishna aside to convince his father to let Padmavati complete the final rites of her son (if it was up to Vasudeva, he would probably hang him up for the public to see!).
Krishna, as we see in the next parts of the story, loves Devaki dearly, but it is more of a formal love, rather than the easy, the rather beautifully selfish love he has for Yashoda. He always ensures that Devaki is well-protected and cushioned against all the Yadava drama that ensues after this. We also see the incident in Bhagavatam where Krishna 'returns' her six children to her: I would personally interpret this as Krishna helping her to finally process her grief by constructing a sense of peace and security around her, even in the general political madness.