I'd probably keep offering that afternoon milk for a while longer even if the amount has dropped. It's just that the formula is fortified with all the vits and minerals and solid food/snacks usually aren't so even if she only has a smaller milk drink at that time I'd still give it.
Are you giving a snack where the mid morning bottle used to be?
Are you giving dairy snacks such as yoghurt and cheese? On the one hand these do count towards milk intake, on the other they don't offer as much nutrition as the formula. Depending how much formula she's taking overall you might prefer she had more formula or fortified cereal as a solid snack. You can use formula to make a milk pudding for instance which could then be offered as a snack if she is preferring the solid food to the bottle, or mine had some additional vits from his baby muesli which was fortified but I made it into firmish finger food balls for self feeding at breakfast time (so the cereal was fortified and I used formula to make it up).
One thing I found with my DS was that the more dairy solids I gave him the less formula he drank, as though he knew he'd had enough milky stuff, he was not a great fan of milk and for a while we did better with less dairy solids so that he took a better bottle. Other LOs though seem to take their formula and all the dairy solids are in addition and don't impact on how much formula is taken.
Certainly it's a progression towards 12 months though, a gradual move towards more solids so if the 2 remaining milks are really good ones you might be comfortable for those to remain and for the mid morning and mid afternoon to be snacks or dairy snacks. Sorry, not a cut and dry answer! Like I said, if it was me I'd hold on to the formula for a bit longer yet.