During a play fight my girlfriend "smothered" me and I panicked, now shes annoyed at me

Pretty much what the title says, we were play fighting which we do regularly, but today she got a pillow and put it over my face and playfully smothered me with it, which led me to suddenly panic and start repeatedly saying no and asking her to stop, which she did, but she then got annoyed at me that I would "think she would actually do that to me"- which for the record I dont, I just didnt like it. She then left the room, gave me a bit of the silent treatment and left my house early. What do I do to fix this? I didnt mean to hurt her feelings i just had an automatic reaction.