You decide to hang around for a while. You don't want to risk bailing out while she's walking -- that's just asking for a severe injury (or worse). You're in a relatively safe place for now as long as you stay out of the way of you host's very close and massive buttcheeks.
You manage to scoot up the giantess' underwear toward the elastic band. Your strategy works -- she sits down on a soft leather stool, but you're safely out of the way. You manage to peek out at the vast crowd of young women. You have some time to figure out a plan, but of course it would be best before these partiers drink too much.

One pretty young lady walks right up to your giantess. For a moment, she seems to look right at you. She reaches toward your giantess -- then snaps her exposed panty elastic like a rubber band.
"Owwww!" shrieks your giantess as she jumps up. Her motion and the sudden elastic slackness sends you tumbling back toward the mammoth buttocks. She faces the newcomer with a bewildered look.
"Sorry girl, your drawers were showing," the newcomer grinned. Your giantess returned the smile. "Thanks Keisha," she said. "Sit down and have a drink."
With that, the butt that surrounded you like a giant, fleshy wall now became a giant, fleshy ceiling coming down fast upon you. Both planet-sized buttcheeks smashed down on you, driving you deep into the cushion.
With air rapidly leaving and your body compressing under the warm, but overwhelming weight, your giantess shifted with a satisfied grunt. "MMMmmm, now let's catch up," she said. "Let me tell you about this guy I have a crush on..."