At one point I was doing both bottle and breast because he was a hungry baby and breast wasn't enough, he would pick and choose if he wanted breast or bottle. Lol it was so annoying! :)
My son was like that, nine months old now, turns out he was having a growth spurt, but I would give your doctor a ring just in case, just keep trying to feed her, if your breastfeeding then keep her against your bare breast if bottle feeding take a syringe and feed her. Even though I'm breastfeeding my son sometimes just want to latch, around the time he started teething, had to express and feed him from a syringe
How long has this been going on?
Take her temp too and try just giving her a couple ounces of water. You don't want her to get dehydrated but sleeping/sluggishness is a sign she could be getting sick
Could be teething, or an ear infection or she might be starting a cold. Its hard to know for sure but you should call the Dr. She's definitely not feeling well and when they're that little its better to be safe than sorry