Flight or Flight Response?

Lately, my mom has been grabbing my shirt or 'playfully' hitting me. But it makes me very uncomfortable. I always flinch and she gets mad at me when I do. She says that I act like I'm afraid of her and she says she doesn't deserve my reaction.

But I have no control over it. I get scared very easily.

Not 15 minutes ago, she grabbed my shirt and I went into a panic mode. I tried twisting to get away and I felt my heart beating quickly. The only thing I could really think was "I have to get away". I ended up hitting her in the arm. Not enough to leave a bruise and I doubt it even hurt, but she yelled at me for it and has been angry ever since. I tried apologizing, but she still just keeps bringing it up and saying I shouldn't have done that.

The only thing I can think of is that when she does this, I feel trapped, and my fight or flight response kicks in. I'm used to flighting, but since I was trapped, I went for "fight" instead and ending up hitting her.

I just hate it because I know she's going to do it agian, I know I'm going to react badly again (either by flinching or hitting), and I know nothing I do can convince her that I don't mean to do it.