AIO Girlfriend Ignoring Me Until I Buy Prom Dress

Background: I have been dating her for 5 months and told her that most girls wear short dresses to my prom on a cruise (we’re both over 18). We go to different schools and she’s never ignored me before and is usually obsessed with me

IMPORTANT – WHAT HAPPENED ON FACETIME: I told her that I found out that the dress is allowed, but she said that she’s now wearing the blue dress to her prom and putting the black dress in the closet to wear somewhere else. She never showed me an image of this black dress. She wants me to now pay for a new short dress. I told her that yesterday she said she wants to stand out and be different even though everyone is wearing a short dress even though it’s not allowed, but now she won’t wear a long dress (it’s the next day she’s saying all this) because she says she’ll feel uncomfortable and above everyone else standing out even though I told her that around 20% of the girls wear long dresses and she won’t be alone. We tried debating but she wouldn’t listen to my side and she said “someone else is calling me” and then hung up on me, but no one was calling. I do not want to buy her a short dress now that it’s not required.

WHAT HAPPENED AFTER: After sending the short update to the interview, she ignored all my texts and photos I sent, even the one I passed out. I was on my senior school trip. I was advised by my friends to stop sending updates since it seem that I was chasing her. It’s been 4 days and she’s still ignoring me and she even stopped sharing her location with me and opening up snaps and stories.

I feel that she’s just waiting for me to give in to buying a dress and ignoring me since she knows that it will hurt me. Is this an abusive relationship and a major red flag?

Please give me your opinion