V.B.
If you're trying to wean from the bottle at the same time, I would just go ahead and introduce the milk in the sippy cup. You also don't need to use formula if you want to mix half and half, just pump and use breastmilk if you would rather her have that. My daughter wouldn't drink milk from a sippy cup for a long time. We tried every kind out there and she just wouldn't do it, so be aware that this might be a problem. She would drink water out of them but not milk! We ended up having to give her milk in a regular cup and she would drink it that way because she also took forever to learn how to drink from a straw. It was really messy, but at least we got some milk in her!
My daughter weaned herself at 10 months old. She also stopped eating baby food and wanted table food. I think she just got really independent all of a sudden and just didn't want anyone feeding her anymore. She was using a fork and spoon by the time she was 13 months old! Anyway, good luck with the weaning process. My daughter made it pretty easy for me and it sounds like you won't have any problem either.