Way to confront friend...?

Long story: Recently, some friends and I took a trip to Vegas to celebrate a friend's birthday. We agreed that it would only be 4 of us. Anyways, one friend says they can't make it until very late in the evening due to work (we're only gonna be there two nights) so the others and myself pitch in to pay for a late night flight so she can make it out. Anyways, day of, she MISSES her flight despite having four hours to make it to the airport (she lives in Los Angeles btw). The next flight isn't until early in the morning so she then says that her boyfriend will give her a ride to Vegas but she insist that he spend the weekend with us. This made the rest of us uneasy since we all agreed to only close friends and now we had to share a suite with someone we didn't know.

On top of that, they argued to have the one king size bed to themselves and mostly treated the trip as a romantic weekend getaway. The rest of us feel angry since we bought her a plane ticket but almost seemed to miss it on purpose only to have an excuse to bring her boyfriend.

How can we tell her how we feel without becoming hostile? It almost seemed like she did this on purpose so how can we confront her with that?