a couple things, how did you go about switching her? was it all at once or did you blend the old and new foods together? Is the protein level in the new food higher or lower than the old food? How long has she been passing this new version of her waste?
Changing food can cause all sorts of weird things gas and change in look/feel of waste are common things. You mentioned she has allergies and that is the reason for the switch is it possible the allergies were effecting her bowel movements before and the "new" ones are actually more healthy ones that you are not used to?
It doesnt sound like anything to be too worried about I would call my vet if it really worried me, if only for peace of mind.