We went through a babywearing strike around that age, too. Is she fighting 'practicing' the back carry or being worn in general? In our case, DD hated trying new carriers as well as practicing new carries (in our case, wrapping). She'd run away crying, "no, Mama, noooooooooo!" I gave it a break for a while, and now she lets me wear her again.
It also helps to have a fun toy or a snack while we're getting in the carrier. Maybe also get her a doll sling so she can carry her 'babies'? That might spark her interest in babywearing again? DD also seemed to become more interested when she saw other babies being worn.
Hope your DD gets back to babwearing soon!