Lily,
If you don't have a prior relationship with Caesars or MGM to take advantage of comps, call a property you are interested in staying at, tell them your intention to do a bachelorette party, and ask what their group rates are.
As for things you can do in Vegas, I'd recommend three things:
- do a casino crawl, where you go down at least one section of the Strip, into every casino, and get a drink and a #1 chip. It is a fun twist on the pub crawl.
- have a list of embarrassing things she needs to do that night, like serenade a random stranger, dance the lambada with a random guy, ask people to sign her shirt. Take lots of pictures.
-Get her some adult entertainment, like taking her to Thunder From Down Under or Chippendale's or something like that.