Theory: From Jinx's point of view there are next to no upsides to being Powder other than that Vi would love her.
1.) Powder was already mentally ill as we can see from the scene opener where Powder on the bridge has similar hallucinations to what Jinx has. The enemy music video also suggests this. So "going back to when I was not mentally ill" is not an option/an association in her mind. Powder was already suffering from mental illness.
2.) Powder to me comes across like a shy kids who didn't have many friends. We only see her be friends with Ekko and I would suggest that body language in the Enemy music suggests that maybe it was initiated by him. Plus we know based on his Firelights that he's a naturally social person. So "having friends" might not be an argument in Powder's favor in her mind because Powder already was somebody with few friends outside her family. so pretty similar to the situation Jinx is in.
3.) Jinx is a brutal criminal, Powder wasn't. But we don't know for sure that this really matters to her. I would argue that various camera choices suggest that Jinx enjoys at least the cat and mouse part of her violence. And the fact that none of her new victims (Firelight girl, enforcers) join the chorus of voices in her head suggests to me that she does not feel bad about these crimes the way she feels bad about the deaths of Claggor and Mylo. Like if every crime caused her voices, her hauntings to get worse, I would agree, going back to not being violent, not adding new voices would certainly be of interest to her. But that doesn't seem to be the case. Also note that Episode 2 Powder wanted to put nails into her bombs to kill enforcers:
In the enemy video she's also seen fantasizing about taking down enforcers as Jinx.
4.) Both the enemy video and various Act 1 events suggest that Powder was unhappy with her life and felt weak. This is something that bothered her even before Silco came along and added his own "overcoming weakness" ideology.
IMO Jinx has wrapped a lot of her guilt over Mylo and Claggor up into Powder. While it would certainly healthy for her to face those guilt, I think it's understandable that doesn't want to/shies away from it. Especially when from her point of view there are not that many upsides to "being Powder"/"living like Powder again" other than "Vi would love me again like she used do". (ie it's probably highly doubtful in her mind that Ekko would love her again like before because her various Jinx crimes still happened)
So from her point of view, being Powder means doing something she doesn't particularly want to do (experience her guilt) just to be somebody she doesn't want to be (a mentally ill, weak girl who has troubles connecting to others, also somebody arguably worse equipped to handle the violent world they live in) with the only upside being Vi loving her.
IMO Vi has very positive memories of Powder (and so do we because the show is largely told from Vi's perspective), but she didn't actually have to be Powder/she doesn't know what it was like to be Powder (IMO the Enemy video comes closer to telling the story from Jinx's point of view rather than Vi's). So Vi's view on Powder is probably a lot rosier than what Jinx's view on Powder is.
My take is that Powder was already pretty unhappy with her life and that being Jinx allows her to do things she already wanted to do as Powder but wasn't capable of doing.
Note that that is less "Powder and Jinx are separate personalities that Jinx and switch back and for of" but more "Jinx has good reasons for why she isn't too keen on accessing the more Powdery aspects of her personality".
I think there is a way to view Jinx as a bit of a coping mechanism (even if not a terribly healthy one), but not just as "she wants to avoid the pain and guilt of having killed Claggor and Mylo" but also "it makes it easier for her to be confident and do the things she years to do and come out of her shell" (think ... Beyonce and Sasha Fierce maybe).