First off, a belated welcome to this forum!
I also want to apologize for the fact that your post has virtually been ignored on here.
I have to tell you that the story you have told so far just breaks my heart.
I'm going to be very blunt and to-the-point with you...at the same time I want you to understand that I'm not criticizing you.
First, you need to understand that your little cat, if she were human, would now be 76 years old. That's OLD.
It means that she needs more attention now than she did when she was young - and even since she came to be with you.
Now, you said she's your cat. THAT makes YOU responsible for her. You also said that your mother is somewhat involved. To be honest, it sounds like your mum has a better awareness of the cat's condition than you do.
Your cat is going to need to go back to the Veterinarian - no matter what.
No matter what...whether it's going to be for examination and further treatment...or to be put to sleep.
That's where my first question comes in. Are you financially able to get further treatment for her?
If you are not, then, judging from what you have described her condition to be, the kindest thing you could probably do would be to have her euthanised.
If you have the financial means to have her treated, then I will ask you if you are willing to do that and, if you are willing to put the time and effort into taking "better" care and concern for her than what you have done so far.
Now...remember, I said I would not be critical. So, let me explain why I said what I did just now. I cannot understand how anyone who expresses concern over their cat would allow the cat to get into a state where she smells, has feces on her hair and is allowed to go sit out in freezing cold or hot. Again, in all honesty, I'm not criticizing...I just don't "get it".
Actually, I just realized that you haven't really expressed any concern at all. In fact, all you said was
|i donâ€™t know what to do
So, for starters, let me return the question to you. Based on what I said, what are you ABLE to do and what are you WILLING to do?
You reply and I'll get into the medical stuff with you.