Is it normal to get very upset when a girl is ignoring me?

You need to get out of your depression, she is ignoring you because of the way you act because of the stress because of other problems you face. Start from the right and cross out your problems until you see the word her and then she won't ignore you(most likely).

What if a guy is ignoring you? What would you do?

Rejection hurts. It's hard to deal with someone ignoring you. Maybe they're doing the wrong thing? Maybe you could try to think what upset them enough to make them ignore you? Could you or 'they' have acted better and not so mean?
Time is a good healer. Don't beat yourself up about it. There will be lots of times in life when you just don't get why someone is acting that way towards you. In the whole scheme of things in the world - it will seem quite small one day, and not worth hurting yourself. Take care.

You need a better way to deal with rejection.