You are and have been feeding her regular food, right? A lot of responders have taken "exclusively breast fed" to mean that you're not feeding her food, but I took it to mean that that was the only kind of milk she was getting but that you are giving her adult food as well. Is that correct? She does need to be eating regular food at this point.
I give my little girl (21 months) an 8oz bottle of fresh cow's milk at bedtime and she's fine. She usually drinks all of it, but sometimes falls asleep before she finishes it. And I am assuming that when she nurses, it is more for comfort than for nutrition at this point, is that also correct? So it's not like she's getting 16 oz of milk before bed or anything, right? Because if she was, I'd have to agree with the other moms that that is TOO MUCH.
Now, more about the milk--is what you're giving her regular milk (as opposed to grass-fed/ organic?) Maybe that's making her sick. Some children have bad reactions to regular milk b/c of the hormones or the feed the cows are given or even the pasturization b/c it kills the enzyme lactase (which helps digest the lactose that many people are intolerant of) Did she do this before you switched off the breast?
From my experience, I think that when she was waking up in the middle of the night to nurse it was probably more of a comfort thing than a hunger thing, so you probably don't need to load her up before bed.
Vomiting may be a control issue with her. It certainly gets a big reaction! What do you think it is that's setting her off? Is it simply that she doesn't want to sleep or could it be something else? Maybe she's protesting because she doesn't want to be alone.
You might try forgetting about the extra bottle for awhile and try rocking her/nursing her to sleep. You said that she used to fall asleep on the breast...would she still do this? Maybe it would make her calmer and then you could just lay her in bed.
Good luck.