She says something like, "I have to get back. He'll wonder where I am..."

Sure- it could be Sawyer-- or some other new guy...

Could she be refering to her child rather than a mate? Like-- the baby is with the sitter and if I'm not there if/when he (a toddler) wakes-up, he'll wonder where I am...

That would certainly change her perspective on needing to get back to the island.

My guess is that after a crazy international chase of her as a fugitive, she would HAVE to be in hiding when she came back-- after killing a US Marshall. That might also explain some of her furtiveness.

Just a thought...