She may need more time to grow up, but she is 20 years old. She isn't a kid in high school trying to fit in with a bunch of kids.
I think it is time to put your interests first. You have put her first her whole life. Now you have to think about your future.
Of course she will meet people at work. That is were many adults find friends.
I am a little concerned about the 55 and up community. My mother in law lives in one and except for the kids that come visit. There isn't any.
Again, she is 20. All she needs to do is find one friend her age and it won't matter that all of her neighbors are older.
I think you should go for it. It is time to think about you.