J.B.
We have patients that have this issue all of the time. I would wait another week or two and see if her tummy adjusts. If it is getting better with gas drops, then it is not bad enough to confuse her digestive system just yet and switch formulas on her. If you do decided to switch, or after 2 more weeks still see her having the same issues, try Enfamil Gentlease. (Nutramigen is really for babies with severe issues) (like reflux, etc...)
My daughter was also very gassy her first few weeks and had colic. It went away around week 5. She is on Enfamil Gentlease still to this day and we rarely ever have to use gas drops.
But, remember every baby is different and you should do what you think is best for your baby.
Good luck!