Hailey Bieber Wilds Out with Kendall Jenner at Bachelorette Party

Hailey Bieber's a sucker for monstrous penis-shaped cups in the hands of friends like Kendall Jenner -- 'cause when you're the bride-to-be everyone does as you please.

Hailey, Kendall and several other friends were wildin' out Wednesday night in L.A. for Mrs. Bieber's bachelorette party. They started the festivities with dinner at Ysabel, and then made their way over to Delilah nightclub in WeHo.

In the pics, you can see how delighted Hailey was at the sight of Kendall working the phallic sippy cup. BTW, the straws were also penis-shaped, so ... pretty much every bachelorette party you've ever seen or attended.

Hailey was rocking a strapless, bridal white dress, complete with a veil, diamond necklace and, of course, her blinding gigantic diamond ring. Hell of a sendoff just days before she and Justin Bieber walk down the aisle in South Carolina.

TMZ broke the story ... Justin and Hailey locked down their wedding singer -- Daniel Caesar. You'll recall Justin and Hailey got married in an NYC courtroom last September, but this ceremony -- for family, friends and God -- is equally important to them.