I wouldn't stress about 200mls of formula a day. At that age DS2 was still having 8-12 breastfeeds in 24 hours.
Formula has far more nutrients than cows milk (or equivalents) and at 18 months she should be having 1.5 serves of dairy. 1 serve is 250mls of milk. So I think the formula is fine!
I wish DS2 would drink toddler milk or similar. It would be such a relief to be honest.