I never thought about her having empathic mimicry... I don't think she does; she'd have been way more effective. She'd be able to fly, she'd have Adam' self-healing, she'd have Bob's alchemy (meaning she wouldn't have to steal socks...

) and Linderman's healing... and a dozen more things. I can't imagine that that is it.
Didn't the producers say at one point that she had a similar power to another hero, only that it was easier for her to get what she wanted? I always wondered about why she touched Heidi so much when she talked to her outside Nathan's hospital room. I think it may be some kind of persuasion. It's also something Peter might have used without us knowing - we may have thought he was mainly persuading another person in the normal way.
I'm really thrilled to find out more about Mrs Petrelli. She's one of the most intriguing characters in my opinion.