It can be exceedingly difficult to tell if a hedgie is pregnant just by looking at her. And, at 10 weeks, discerning between is this normal weight gain vs pregnancy weight is going to be pretty much impossible. All hedgies do have nipples, so that's normal.
Here's what I'd do: I'd consider it possible that she's pregnant. Per HHW: Typical gestation is 35-38 days, HOWEVER, you need to prepare for possible delivery anywhere from 30 days from first breeding chance to 50 days from last breeding date. So, figure that she could give birth between about 30 days since she turned about 6 or 7 weeks old and 50 days from the day you brought her home.
Take some time and read up on things. I'd recommend the articles posted in the stickies her on CnH and the info on HHW:
http://www.hedgehogworld.com/content.php?216-Breeding-stage-1-Conception-to-28-days-gestation
http://www.hedgehogworld.com/content.php?217-Breeding-Stage-2-28-days-gestation-2-weeks-post-birth
At best, she's not pregnant and, after you read through everything, you'll know a lot about hedgies. Info is always good
At worst, she is pregnant (never good to be a super-young momma hog), but you'll be prepared.
Was there anything at the breeder/pet store/place she came from that feels more or less worrisome/reassuring about a possible pregnancy? For example, if she came from a long-standing breeder with good practices (say, like Nancy on this forum), I wouldn't be worried about pregancy. But, from other sorts of places, I might be more concerned.