Am I in the wrong

Me, 19M and gf 19F have been dating for 2 years now. I have strong morals and I absolute despise cheaters and just lying in general. I'm currently at uni studying business management while my gf has been job jumping the last 2 years and now settling for the ADF (Australian Air Force). I recently went to catch up with a few friends. One that wasnt doing 100%. (Parents divorced, fumbled a girl he really liked). Me being a friend wanted to give adive and asked what happen. Mind his M19 as well and has pretty good looks. He showed me a picture of her and i mentioned that she was gorgous and asked what happened. The convo went on about how he was just dumb and didnt see the hints blah blah. Me being me i always let my gf into whatever shenanigans me and the boys talk about, if theres gossip or not. I mention that i was trying to help him out and that the girl was gorgous and they would be really good toegther. Well anyways my gf didnt appreciate that. Started telling me that because of that comment i see her as a "lesser girl" and told me to "fk off". She said that i cant compliment other women and I had to stop her there. I tried to reassure her that I was hers and that its okay to compliment someone. My parnets have been married 30 years and constantly compliment the opposite gender. Not because they are into them ofc but to genrally give a compliment. Mum: "how was your friends wedding, how was the bride"...Dad:"they were gorgous" and so on. Me being a very understanding bf, again i was there for her during her lows, her job hunting and supporting her all throughout the process. Even with the idea of her having to go away for months due to the air force. I had to understand that, that was what she wanted and that i had to be okay. I really supported her and love her and am extremely proud of her. However because I called a girl gorgeous she has threatened to leave and stay in the army to never return, that she dosnt belive I love her and that I have degraded her. I really need help with getting another point of view because I really am stressing. I do care alot about her. She claims she isn't insecure and I have asked her to open up but claims that what I did was just wrong?? I'm just here to learn something