Recruiting Vanilla allows access to an item store. Complete stages of her side quest to access a larger inventory. Keep in mind that entering New Game+ resets her inventory expansions.
Vanilla: Welcome to the Monster Lord branch of Vanilla's Shop! Even friends have to pay, no exceptions from us merchants.
Rami: "My breasts are so heavy I can't fly..."
Vanilla: "That's all you have to say? Go to hell."
Rami: "Waa, so cruel! That's not nice."
Vanilla: "Having to look at THOSE is not nice to me! They're enough to make me cry..."
Teeny: "Still flat..."
Vanilla: "A perfect washboard..."
Gob: "Vanilla, I found a star-shaped stone. Here, it's for you!"
Vanilla: "Waa, such an unusual stone! Kukuku, it must be very valuable."
Gob: "No, it's just a plain old rock from over there..."
Vanilla: (Ho-how would you know!? I could get a lot of money out of it."
Papi: "Rawr! One of my fangs fell out! Is it molting season already?
Vanilla: "Give it to me so I can put it in the shop! Dragon fangs fetch a high price."
Vanilla: "Ah... Your claws are so long too, I'll cut them for you. They're worth a lot, and your scales..."
Papi: "At this rate, you will sell my entire body..."
She is required in the "Amira's life advice" and "Tiny Bandit Game Club" scenes.