I think that it is no justification for her self isolation, but there are probably 10 times as many people or more that do exactly what your mom does only they do it with TV. I don't think you can fix her behavior. That is up to her. You are in your very last days in the household. When you leave, the problem will stay there if you don't take it with you. You can express your concerns, but your mom is an adult and entitled to do what she wants to with her time. I think any effort to manipulate her to better suit you, or others, is doomed to make the problem worse, not better.

OK, that said, you have to know that I am not too different than your mom. I have a very hard time with normal socializing. Doing it on internet is a life saver for me (including this site). I do think my family has learned to cooperate with each other's needs a bit more pleasantly, though. We each have our own computer. They are very cheap these days and it is not much different than having more then one TV in the house.

You have come to an age where you clearly realize your mom has flaws. It is disappointing. It is ok to let her be flawed. It sounds like her behavior is annoying, but not really all that bad in the grand scale of things.

How many therapists does it take to change a lightbulb? One, but the lightbulb must want to be changed.