It is totally up to you! If you want to quit breastfeeding, do so. It won't make you a bad mom, and you should not feel guilty.
Also, don't get scared about your baby's weight at this point. She IS gaining weight. If she were losing a lot, it'd be one thing, but her weight is going up. Don't let the doctors scare you. What is important is her disposition, and that she is having lots of wet and poopy diapers!
If you are interested in continuing breastfeeding, I do have some advice for you. It sounds like you might have two issues going on, judging from your post. With your daughter not taking a bottle at daycare, would your daycare provider try other methods, like a small cup (a shotglass is the perfect size), an eye dropper, or even just a straw with one finger used to create suction?
Also, have you seen the Adiri brand of bottles? They basically look like a breast. They are one piece (even the nipple). Google "Adiri" and they should come right up.
Have you tried breastfeeding right at the daycare, when you pick her up or drop her off? Can you go see her at lunch?
As for your supply of breastmilk, I never got the same response from a pump as I did my baby. My supply really dropped the more I pumped and the less I actually breastfed. I also drank a ton of water and the "mother's" teas. I meditated and prayed and relaxed the best I could, but it wasn't the same. Breastfeeding doesn't have to be "all or nothing". If the amount you are pumping seems of value to you, then continue. When I stopped pumping, I was only coming home with a couple of ounces each day--it totally wasn't worth it to me. It's really your call. Just listen to you heart on your mama instincts on this one. Good luck.