I think this is one of those things that is completely up to you two and how you're willing to work it out.
Would you split the profits 50/50 or she collects hers, you collect yours?
That's where it can get tricky.
I have 2 niches in my shop, both by myself, I crochet and stamp metal, so I have them both in my shop, and both do equally as well at different times of the year [so far].
So essentially, come up with a business plan together and see if you can make it work.
Good luck!
And hey, her items could sell your items and vice versa, right?
:)