I have owned a red-eared slider for about 7 years, since I was about 10 years old (I am currently 17). I will shamefully admit I have never taken care of her well, and she's currently living is less than proper conditions. I really want to improve her situation, but unfortunately I currently have neither the money nor the space. I want to make it clear that I really do want to keep her, provided that it is the best option.
Her name is Bee, and she's probably around 7-8 years old and about 7 inches long. I currently have her in a 20 gallon tank (I am fully aware that it is incredibly small tank and is not nearly enough for her), no filter, and as of now, no basking area (it was a cheap thing that broke a few days ago). There is little to no proper lighting, but I do take her outside for the sun every now and then. She eats healthy, though (regular feeding of romaine lettuce and pellets, occasional fruit). I have no idea if she has any health/shell issues. I know it's far from ideal, but unfortunately my options are limited (very little, if not no one, is willing to adopt her from me in my area, rescues are full, and euthanasia is probably my only other choice).
I would appreciate help on either what to do with her, or how I can improve things so they aren't completely awful until I can afford buying a proper tank/filter/etc. I am looking to buy a 150 gallon tank and a Fluva Fx6, plus all the other necessary items such as a basking area, UVA/UVB bulbs, etc. However it may take years for that to happen, and if it is the best option to give her up, I'd appreciate if anyone helped me.
My family owns a 50 gallon tank that Bee will eventually be moved to, but that won't happen any time soon because it's currently housing fish. I hope this doesn't sound too desperate I've spent the past few years being a terrible owner out of ignorance and apathy, and I want to change that...