Have you tried expressing into a sipper cup? I would say at 6 months is the time to start weaning them off a bottle anyway, so just see if she will have it from a sipper cup and if you give it to her with your milk in it, the childcare staff or babysitter may be able to give it to her even if it doesn't have your milk in it. Or try giving half and half with your milk and other milk for a while in a cup.  worth a try, my daughter had a cup from 8 weeks with water in it so it's not impossible, she never had a bottle. It just takes time and persistence.  You can always combine the 2, give the formula in a cup at daycare, and she will have to have it because you're not there and just breastfeed at home.  That's worth a try too.  The worst that will happen is that she will prefer the formula in the end, but that's what you want anyway.  Good luck with it.

Depending on how old your baby is (ie around 5-6months) you maybe able to teach her to take a trainer cup instead. I did this with my second son who wouldn't take a bottle. It will take persistance but they do get used to it. Simply start with small amounts so they don't drench themselves. Also you can get cups with soft spouts which are easy to drink from. Hope this helps! Then you do away with the bottles altogether.

Have you tried expressing your milk into the bottle so it tastes the same??

Someone I  know put bandaids over her nipples & told her daughter they hurt - won't always work but jut thought I'd mention it!