We didn't actively wean either. It just happened. If you feed on demand, just offer formula when she's hungry between meals but not if she isn't. If she's eating well during mealtimes, she's likely to be less hungry between meals and will take less and less formula, eventually she won't want it altogether at a particular time or will take so little (maybe an oz or 2) that you might replace that bottle with a snack. In our case, probably around 10 months or so, our daughter wasn't really interested in her mid-morning (about 10am) bottle. She just didn't give hunger cues and would make it to lunchtime without needing it. So we just starting going straight to lunch around 12 and then I'd offer her a bottle after lunch instead. Slowly, she stopped showing interest in a bottle between meals during the day and by about 13/14 months, she was just having the morning one (though by then it was a cup of cow's milk) when she woke up after which we'd have breakfast and then a cup of milk again before bedtime. Around 15 months, she dropped to only a bedtime one and that's what we still do now. If you are keen to encourage her to drop a bottle, you might try adding in a snack at that time and then offering the bottle after. If she's still hungry, she'll take it, if not, she won't. But I think in time, you'll find it just happens on its own as she's eating more and more solids.
