Ya know my headcanon is that Mels didn't exist in the childhood they actually lived, instead it was in their childhood of big bang 2 where Amy had parents. Which Amy says (in a minisode) that her life doesn't make sense because she can remember both her childhood without parents and her childhood with parents. My full idea here
But River says in her reveal episode "The Doctor will find your daughter, and he will care for her whatever it takes, I know that, It's me, I'm Melody, I'm your daughter."
Stick with me for a hot second.
Melody is kidnapped at demons run and sent back to the 1960s abandoned orphanage. She escapes the orphanage, gets "eaten" by the space man, escapes again, and ends up as a little sick girl in New York City. Shes dying. She regenerates in 1970. Then somehow by magic she finds her parents in the UK in the 1990s still a little girl and ages at a normal pace with them through school. Thats at least 20 missing years.
Possible explanations are
0.)Magic spell that deletes plot holes
1.)There is a regeneration between Melody and Mels who lives through the rest of 70s and 80s, finds where her parents are in the 90s, and then forces herself to regenerate into a little girl once she finds them. Plausible because Mels said it took her awhile to find them. Edit: Actually in Lets Kill Hitler she said the last time she did this (regenerate) she became a toddler in New York. So The Silence would have had to get Mels again to program her mote before she went to the UK??? Or she regenerates twice in New York but that seems less likely
2.)The Doctor finds the newly regenerative Mels in NYC, potentially passed out in an alley (since we know regeneration can do that) takes her to the TARDIS, travels to 90s, leaves her in the correct town in the UK where she will be enrolled in school with Amy & Rory. This still fits with the second childhood theory and fills up the missing time between Melody and Mels.
While the first one seems more plausible, I'd like to think the second one is correct. It also explains why Mels so weirdly angrily obsessed with the Doctor. The Doctor shows up to her in 1970 when she's a little girl, whisks her away to the 1990s UK, and just leaves her there, never to meet him again until shes an adult (which near perfectly mirrors Amy)
If the first one is correct then The Doctor says "on my life she'll be safe" in optimism that heartbreakingly River knows will not happen thus River saying "he will find her, and care for her whatever it takes" is a lie. They both lie we know this. All that extra searching for Mels The Doctor does could be a show for Amy & Rory. The Doctor did find her, and allowed Mels to grow up with her parents in a relatively safe and comfortable life. And then even after LKH he leaves her in the "best hospital." But he was also surprised that Mels was Melody/River, again easy to wipe away because of just how good the doctor is at lying especially 11
#1 is probably correct and much darker. #2 Needs a lot of lying on the Doctor's part, and for the second childhood theory to be true, but its much nicer and kinder to River with less tragedy in her past
And I did check TARDIS wiki for extended media explanation and there doesn't seem to be anything filling in the 20 years between Melody & Mels
