You could change the formula if you want. However, I don't think a little syrup is a big deal...that is, IF you get a little sneaky. Your daughter has associated the addition of the syrup with "yummy." OK, "damage done," so to speak, but it's all right, it happens. Doesn't mean you have to comply and add a huge chunk of syrup, though. This may sound a little mean, but you can "trick" her (like I did with my son). I would "add" just a few sprinkles of Nesquick -- JUST enough to give the milk a pink tinge (this was when hewas a toddler would refuse to drink milk unless it was "sweetened"). I mean, literally, about a quarter of a baby spoon or even less was more than enough. At the same time, I would "show" him that I was adding it if he got suspicious and would look at me while I prepared his bottle, you know, to make sure I was adding. So, I would start adding, showing him a small lump of Nesquick on the spoon, and then, distract him and very quickly remove a large portion and add only a little dribble to give the appearance of pink. And I found that this was enough to get him to take his milk without a problem.
I let this go for a few months, and then started to wean him off the Nesquick. So, I would give him milk with something else he liked to eat. In order to eat what he liked, he had to drink the milk the way it was - only choice I gave him was to warm it a little. At first, he protested - but he eventually got the idea and now he's fine.