J.
This confusion can definately happen. (I've nursed 3 kids and I swear I feel like I've seen it all!!) Also, you may want to check and make sure the bottles you're giving her have the smallest holes. This will more closely simulate the breast since the baby has to 'work hard' to get milk out of the breast unlike the bottles with the larger holes. If she's been using the bottles with larger holes she is probably getting frustrated that your breast doesn't flow as fast. Keep it up!! She'll be fine. Especially as she gets older/chooses to eat more solid foods and won't take a bottle as much, but will still LOVE to nurse.
P.S- No 4 month baby I've ever seen doesn't 'not want' to nurse....you may want to look on Kellymom.com for more information, it's really useful in cases where the baby is on a 'nursing strike' due to stress, etc....good luck!!