A.R.
If you have a nagging feeling that something isn't quite right, go with your gut instinct and take her to the pediatrician. She may have a sore throat or earache that makes it hurt to swallow- however, if she is not crying and fussing, I doubt that is the case.
I do agree with most moms here that if she is hungry, she will eat, and I went through this with my own daughter (but at 4 months old instead of 8 months) and it lasted a couple of weeks and then all was back to normal.
You know your child best though, so go with your gut and get her to the Dr if you are really worried.
I would not worry that you are "training her" to take a bottle in the middle of the night... if she needs the hydration and wants to drink, I personally would let her.
-Amanda