Is it a good idea to get a cat that has lived alone for 5 years a friend?

I have a cat who is 5 years old and has lived by herself with me for the entirety of that, and we're both very happy. She is indoor only, but she has lots of toys and I give her lots of love and attention. However, many people around me are urging me to get her a friend so she won't be lonely. She's a very opinionated and independent cat, so I'm really not sure how she'd react. I think she's very happy being the only cat, but I'm not sure if she'd appreciate a feline friend or not, especially while I'm at work or with family and friends.

Is it a good idea to get a cat like this a friend, or are they generally happier being the only cat? I don't want to uproot her life, but I also want to enrich her life in any way possible.