Does she seem to be acting normal otherwise? The feeding charts at the Enfamil website indicates she should be taking 24-32 ounces per day. I'm assuming she was drinking close to that prior to 3 days ago? Is she eating more solids than usual? Maybe she's just going through a phase and will get back to normal within a few days.
I can remember many days when Cody would barely take a bottle, especially when he first discovered solids. Then he'd go through phases (and he still does) where one day he prefers formula, another, he'd rather have food. I used to notice it particularly after he had a little growing spurt. He'd drink up to 40 oz a day for a few days, then cut way back for a few more.
Perhaps it wouldn't hurt to call the doctor and ask their opinion. It would probably put your mind at ease. I'd love to hear how it turns out. Keep us posted!