D.B.
I exposed my boys to the sun early on and didn't really worry about the amount of time they were in it...just had them in a hat and only put baby sunscreen on their arms, legs and face if they were swimming. Otherwise, if they were playing outdoors, they just had a hat, t-shirt and shorts with no sunscreen. Mornings are usually best as the sun is the hottest around 2pm-4pm. I don't think you really have anything to worry about unless your baby has a very fair complexion, which it doesn't sound like she does. She doesn't need to be naked with only a diaper to enjoy the benefits of the sun. No need to worry...just have fun playing with her outside and not be so strict with staying to the 30 min/week. My boys were outside playing for at least a couple of hours every day at 6 months with no problems. Have fun!