Why won't she reply and what do I do?

This girl I like has stopped replying to my texts, but I don't know why. I don't know if I've said something wrong. I've noticed she's tweeting so she must be looking at her phone, so I think she's ignoring me.

I just wondered what the reason could be and what I should do.

I don't want to keep texting or try calling her in case that makes things worse.

This is making me crazy, because I really like her and think I may have upset her.

Sorry to be blunt, but it sounds like she doesn't want to talk to you. Just leave her alone.

Without context, we can't begin to guess at WHY she's stopped responding. Did you send too many texts and she got tired of them? Did you say something to upset her? Is she not that into you? Could be many reasons.

What's happening in real life? Do you take her out or spend real time with her?

Give us some background

I'm a male but this is obvious cause there is only one answer. You have to stop texting, if she has any interest she will wonder why u are not chasing her anymore and texted u back. If she doesn't text you back you have your answer, not interested at all. Your only option at that point is go to a place she hangs out and "accidentally" run into her but wait a couple weeks. If that happens do not bring up her not responding just say hi, a little small talk then go hang out the rest of the night with friends. Good luck.

Be patient. Wait for her reply, if she still not replying that only mean that she don't like you. Sorry to tell you this.
But i think she don't want your company.