What do I do about my business partner who wants to leave the business?

I co-own a little sexy underwear shop with this girl named Erica and we have a lot of women and men coning in. My business partner wants to leave cause she feels like there's not enough there for her to do

what was her original purpose?

if she is certain to go, have an agreement written up and get her to sign it that you will pay her back
her investment over x months. When she gets all that you agree to, she is no longer part of the picture.

or--why not make the biz a hot sizzling place to be for customers???

why did the first 100 come in and why are 200 not coming in now?

study the reasons for sales slow down!!!

You could have models in --
you could have specialty undies made
you could have special sales

lots of things you can do--and you can change the purpose of the store--I am assuming you have
a fixed site store.

can guide further