Emma Rose is like this -- a mass of small bruises all over her shins and knees. She's had them since she started crawling, and now that she's walking, it's even worse! She's a bit anaemic, and bruising easily is an indicator of this, so I try to get iron-rich foods into her as much as I can to pump up her iron levels. All the females on my mother's side of the family bruise extremely easily -- we'll bump casually into a table one day, and have a huge, ugly black-and-blue mark the next day. So it's nothing new to us.
I'd say, as long as the bruises aren't huge, tender to the touch, or look like they have blood behind them (like blood blisters), it should be something she grows out of as she gets more steady on her feet, and as her body "toughens up". It's not a matter of sensitive skin, it's a matter of her body moving in a new way and her delicate baby legs learning to do things differently. But if she seems in pain from the bruises, or they don't heal, or they really look painful, go visit your GP and get a professional assessment. Or just go for your peace of mind, anyway. ;)