Hamsters groom themselves somewhat obsessively, and at the oddest moments sometimes. A hamster doing a full grooming (cleaning their fur, paws, ears, wetting paws, smoothing out the body fur, contorting to reach those hard to groom places) is usually pretty darn comfortable. Especially if out with us humans.
A nervous sign though is a repeated face washing. If I think my hammy is spooked when out with me, I check to see if its a face wash, or a full groom. Grooming can be a sign of nerves. Which, is often VERY normal. Hams after all are very tiny and we are very big
I'd agree, if she did a full groom she was feeling pretty calm sitting on you. If it were the nervous face wash, its still not a bad thing. She's new. Sometimes outside news, smells, and other things may make them nervous when hanging out with us...doesn't always mean they are nervous about US.
If you look up grooming facts, you'll see a lot of contradictions. The only descriptions that worked for me based on experience is the one I mentioned. You'll find statements that a grooming hammy is a nervous hammy, or a contented relaxed hammy. From what I've seen so far, the face versus full body groom seems to match whats going on with them at the moment....hope that helps.
Oddly enough, my hammies eat less when out with me also, than they used to. They used to debate whether to and always vote for the food. Now, I think they know playtime is not mealtime, and they'll get the treat anyways later, lol. But hamsters are full of surprises....I had a treat prepared for Ziggy today, who find it during playtime and decided not to wait. So much for surprising him. Little booger just stole it....heh.