Went to hang out at the beach with a group of 4 friends. Me and FWB had agreed to go to my place afterwards for some dinner and to fuck. Been fucking this FWB for 7 months on and off, she is part of my friend group.

At the beach, FWB arrives with another guy, this guy apparently offered to pick her up. She told me prior that she would bring him, I was fine with it. I couldn't pick her up, since I was on my motorcycle. I noticed this guy starts hitting a lot on my FWB, she goes with it and seems to enjoy, this goes on for a few hours. She actively engages him, giggles, the whole shit show right next to me.

Around sunset we all decide to go home. I tell FWB to come join me to my place, as we agreed upon. She continues to say she has a headache (even though she was drinking beers) and needs an early night, but we can meet coming week. I had offered her to help her move some stuff coming week, as she is moving into a new apartment. The other guy presumably dropped her off home, or maybe fucked her that day, whatever.

I didn't react to her flirting, stayed aloof and tried not to care. I didn't want to seem butthurt. I don't feel like helping her move her stuff anymore. When I told her goodbye at the beach, I said her I am not sure about "Tuesday"- the day she needs my help to move, she said "oh ok, well let me know as i need to prepare bla bla", I didn't respond.

I know the right thing to do is assert boundaries, soft next, play some dread till she hits me up. I do not want to explain how I think her actions are fucked up and thus seem butthurt. Explaining yourself is for losers.

Even though we both agreed we are good to see other people, her actions are disrespectful. She wanted to make me jealous, get a reaction, she knows I have 2-3 other plates I'm banging. I absolutely do not want to reward her for her shitty behaviour and be her beta bitch. A few weeks prior she made a whole shitshow cause some girl was hitting on me at a party (talking about being a hypocrite).

For now, she lost her FWB status, will demote her to plate even though she is part of my friend group. She pushed for LTR status a few weeks back, I declined. How do I decline helping her move her shit, while not seeming butthurt and continue to plate her?

TLDR: FWB disrespects me by flirting with new guy in front of me, trying to get a reaction out of me. Yet still expects me to be her beta billy.