Don't wait o nthe sippy ... do it now now now.
With Milk being a thinner/runnier liquid than Formula, you will want to be into sippy cups by the time she's on whole milk... otherwise the stuff drips out of the bottle.. so annoying.
Here's what I learned with my kids:
1) get off the bottle before 1year, when they figure out how to fight you about it and hold a milk/formula strike.
2) take your sweet time switching to milk.... transition slowly, and they don't know the difference.
So for an 8oz bottle, say 7 oz of formula + 1oz milk.
then in a few days, switch to 6oz of formula and 2 oz of milk... keep it up for a couple of weeks and that's the end of the formula.
After learning from my mistakes with my older toddler, I switched to a "NUBY" sippy cup the 2nd time around at 11 months...
For two or three days my baby drank 1/2 the formula as normal, but since she eats solid foods like pasta and cheese ,meats, etc... I didn't care...
After a couple of days, she sucked down a 8oz sippy no problem.... no more bottles.
Boy, that is a very different experience than when I switch with my first child late.... I started at 15 months with him... and couldn't get him off until almost 19 months. And then when the bottle was gone he held a strike on milk altogether. To this day, he will only drink milk that is flavored!
GOOD LUCK!