TNR- do you have to release the cat back?

This kitten has been around for about a month. She had pretty feral behavior for awhile but now she’s the sweetest. She’s definitely adopted me & wants to be my cat. I’ve gotten attached & I want her to be too. When I found her, I was trying to get her into a rescue so she can be vetted, rehomed & given the chance to live a loving indoor life since she is so young. Every shelter is full & family, friends, coworkers don’t want any more cats. I’ve had a lot of financial & mental hardship this year, so I wasn’t planning on keeping her because I can’t afford the vet care she would need right now. I’ve had urgent issues with my home & my car & a lot of vet bills for my cats. My youngest kitty was hospitalized in the er twice. My middle needed a very expensive dental procedure. & my oldest crossed the rainbow bridge the end of June. She got diagnosed with end stage kidney failure end of April & we did everything we could. & everything we did gave us another 2 months with her, when the doctor said we would be lucky to have her another week. I feel like this kitten is here for a reason so I can help her. I’m not sure what to do & she makes me feel so bad lately when I go back inside she sits by my door & cries. It’s going to get really cold here soon & our winters are brutal. & I need to figure something out & all I can think of was tnr but just not release her back. Do you have to release them? What if you don’t? I don’t think she’s feral, she just doesn’t have a home. But she definitely wants one.