Entitled Cousin tries to ruin my proposal to my girlfriend

Context: my cousin and me are the same age and this has cause a few problems with use as she likes to compare herself to me this has been going on since I can remember. Cause me to have a not so close relationship with my cousins.

This happened a few days ago and me and my cousin where celebrating our 25th birthday together as my mums side of the family could only all come together on one day. I agreed and didn’t mind we are both adults. I invited my girlfriend we have been dating for 6 years and are happy together. Last year my dad mother passed away and gave me her engagement ring on her death bed a diamond and Sapphire gold ring. I was going to propose to my girlfriend on the party as I want all my family to be there as some of them live in the other side of the country.

We get the the venue and I greet my entitled cousin she smiles at me and looks are my girlfriend “I see you brought a friend. I guess we all can’t be lucky with the boys” (note I’m a happily bisexual female who apart from my parent and grandparents knew I was and I didn’t feel like I needed to tell them this) I ignore what she says and the meal was a lovely success I got to chat with family I hadn’t seen in years and my girlfriend felt welcome into the family as it was clear to see we where a couple.

At the end of the meal I tap my glass and thank everyone for coming and that I had a suprise for everyone I turned to my girlfriend and pulled out the ring. My family gasped and smiled. My girlfriend (know fiancé) said yes and also told me off for the ‘expensive ring’. My entitled cousin glared at me then look at everyone “how can you all be happy for this faggot!” She then turn to her boyfriend I think they had only been dating a few month and tell him when he proposes she want a bigger and better ring than the one my fiancé had. He when quiet and a few family member tell her to be quiet and not ruin this moment. She then storms up and demand my fiancé hands over the ring as “you don’t need it as faggot shouldn’t have nice thing like this” Know I turn to my cousin and get between her and my fiancé “back off ec or ill make you” I growl I’m very protective of my family and my fiancé and won’t take shot from anyone. She goes to slap me to which I grab her arm and twist it behind her back then push her toward her boyfriend. In a sturn and demand voice I asked him to take her home

My auntie and uncle apologised for her behaviour but she won’t be on the wedding guest list that for sure