I was going to see a movie, but my girlfriend caught a cold, and then I said I couldn't go, and then I texted her and she didn't answer.

First, she really caught a cold and was exhausted. She just wanted to rest, so she ignored you. A cold is understandable.

Second, she just has a cold, and the situation is not serious. She could have gone to the movies with you, so she went to work. She said this just to see if you care about her. You didn't see her illness, so you thought she had a bad cold, misjudged her mind, and made her a little angry. But at the same time, she also feels quite complicated. After all, you still care, but you don't understand her so well that she starts to think about whether you are suitable or not, so she ignores you.