So, a girl you like generally ignores you and won’t make eye contact, and you wish to know whether that’s a good sign or a bad one. What are all the possibilities?
She likes you but is doing the OPPOSITE of what you might expect someone to do if she wanted you to approach her and talk to her.
She is painfully shy and wishes you would go up to her but is also terrified at the same time, so she’s avoiding eye contact.
She really does not know that you like her and is completely oblivious to your existence.
She knows that you like her, but the feeling is not mutual, so she doesn’t want to do anything that might encourage you to approach her and talk to her.
I hate to say this, but I’m not liking either 1. or 2. I know some girls play hard to get, but what you’re describing is not that game. The game you’re describing is “sorry, not interested.”
But you never know. Maybe it’s 2. Eye contact or not, if you are attracted to a pretty girl, go up and say hello. If you get the brush-off, at least you gave it a shot. Otherwise, you’ll never know for sure. Whatever happens, you’ll have a better answer than I or anyone else could give you.