You need to see a solicitor with copies of any paperwork you have.
I don't really understand why either of you did this, you gave away half your profit, and she fitted out a shop she didn't own!
Do you have staff? This will affect them and needs to be sorted ASAP.
What outcome do you want? You need to get that clear in your mind first. Have you discussed any problems with her?
Legal help is expensive, so try and talk first.