Feeling out of control is scray for some. Being locked in a room against your will can incite the flight or fight response. I think anger is a natural response to feel trapped. It is the part of our brain that is very instintual, and needs to feel safe and in control.

I don't know the releationship you and her have or exactly how it came off to her. Myself I would have probable kicked the door open if I felt trapped. I'm not claustrophobic, but I don't like feeling trapped for the sole enjoyement of someone else. I think it would also break some trust and I would probable start to emmotional distance myself from them. Then again I generally view the world as dangerous and I either fully trust someone or completely distrust them, that is just me though. That's not really the typical person I think.