Make sure you DO NOT give her anything to drink during the night, not even water, that will bite you later when potty training and a bad habit to stop. Not to mention juice and milk during the night can cause decay and sugar in the juice can wire her out.
If you need to go in rub her back and tell her you love her and walk out, if she cries, as hard as it is that is truly the best method not to go back in. It is self conditioning and it happens so often after an illness. I went through the same thing with my daughter when she got her tonsils out as we had to set a timer for medication three times a night! It took a good month to get back on track after she was all better.
If you reenforce her waking with a drink or picking her up it will never stop. If you pick her up and rock her that will create another bad habit. Make sure she isn't teething either as that can cause miserable sleep, try motrin before bed if she is.
You can reassure her with words and rubbing her on the back and slowly do it less and less each time she wakes. I am not saying do not go to her but change up what you do, just keep it light and simple and leave her awake when you leave.
Eventually she will reset her clock to sleep again all night. At that age if she is getting one good nap during the day she should be getting a total of 15 hours total including bedtime, otherwise being overly tired will backfire too.
Good luck.