Does it mean a girl likes you when she pulls your shirt?

In most cases yes.

Now, how MUCH she likes you can be tricky.

Some girls flirt around just to be a tease, and don't actually care.

She might be trying to get you to strip.

She might just be checking out your chest (in most cases, a flirting way).

She might see a stain and want to clean it!

The best way to find out is to ask her.