I didn't watch it, but if she is a you tube star, it's possible she's making her own money and/or the party is being paid for partially by sponsors. All that really depends on the number of followers she has. Some You Tube stars make a hefty amount. I mean if that's the case, ideally she'd be saving it. But it's also possible that by doing this she could gain more followers, thus upping her brand, followers and paycheck.
I'm sure the car wouldn't be included in there, but maybe she's paying for part of it.
All of this would hinge on if she's actually a You Tube star vs thinking she's a you tube star.