No seriously, I'm actually curious how to handle this kind of situation.
My uncle family has the same problem with their youngest daughter. I'm not really close with them, So I don't know if they manage to fix it or not.
I wonder if someone who study human psychology can give a solution to Rudy's situation.
Her issue is being compared to others and feeling like a failure, even though she's average and good enough.
The solution is usually getting the mind set of being the best version of yourself and stop comparing yourself to others.
Cognitive therapy with finding those automatic negative thoughts and trying to find better, more healthy mind patterns can probably also help.
Otherwise showing empathy and understanding. Doing changes small steps at a time and building routines and habits slowly. Doing things that gives you a sense of accomplishment, and avoid doing things that makes you feel like a failure (can be avoided by taking things slowly, though you'll always need to go out of your comfort zone to improve).
Instead of saying the things that are bad with isolating yourself, like being lonely and missing out on friends and family, developing anxiety and depression, not achieving the things one want in life and not getting an education and work, it'd probably be better focusing on good aspects with getting out. Focusing on stuff like wouldn't you feel better and feel a little brighter if you went out for a walk and did some activity, wouldn't it be nice hanging out with friends and having some fun, wouldn't it be fun doing something that gives your life fun and meaning? Saying things from a positive and constructive way instead of negative and criticism sort of way helps a lot, even though it's in essence the same things being said. It's not always what you say, but how you say it. With empathy and understanding.
It's really hard to help someone who isn't motivated or mature enough to see the point or wanting to help themselves though. Most likely they need to grow and reflect and little before they're able to do something with their life, and see the patterns of how things work. You can't always just say that you'll feel better if you do this and that, they'll need to understand themselves that they'll be better doing this and that. Working with their understanding and what's the main issue so they can help themselves will probably take priority then. In other words, you can't help someone who doesn't want to be helped honestly.