You don't reduce her bottles, milk is her main source of nutrition until she gets to 1, until then solids are for fun! What you will find is that as her calorie needs increase as she gets bigger she will need more solids and her milk will gradually reduce. Most bottle fed babies drop to 3 bottles at around 9/10 months and then 2 bottles around 1 year. It tends to be that the day bottles start decreasing so you drop the mid-morning bottle and offer an afternoon bottle just before her afternoon nap.
You can let her guide you with quantities as long as it's not reducing her milk, follow her full signs.
Sounds like you are doing fine!
Laura