It could be a heat rash, depending on how warm you are dressing her and where you live, it could be anormal baby rash, if you are using fabric softener or even just regular laundry soap you may want to switch to a baby one or one for sensative skin, i know all of my kids got rashes from fabric softener.
Keep your eye on it. My son (1 1/2) has eczema and that's how it started. He was about 6 months old. First it looked like pimples. Then it became larger red patches all over his chest, arms and legs! Is she scrathching at it. Try putting hydrocortozone on it and see if it goes away. Also keep an eye on it and see if any of it turns to little rough patches that get a little crusty or maybe ooze a little bit. When my sons got bad he was given a steroid cream that took care of the bad break outs in a few days. She may also just have some pimples. Perhaps she is still getting rid of some hormones that are in her system since birth. If it remains minimal I would just keep an eye on it until her next doctors appoinment. But I also know that if it is eczema, winter is the worst time for it to pop up! Good luck