yes, when she sings about how "beautiful" the barber was in "Poor Thing," it seems pretty plain that she was in love with him in the old days -- when he was a happily-married young man with a wife and child, and she was not-so-happily married to her late husband. and she did hold onto those valuable razors, too, which suggests a sentimental attachment more than an expectation of his return, given that coming back to England from Botany Bay was close to impossible.
of course, that opens the door to another question: does Sweeney recognize HER when he enters the pie shop?! if so, shouldn't he worry about her revealing his identity, since he's a fugitive from justice and all? for a man who'd be hanged if his identity came to light, he's fairly bold about chatting up his former landlady face-to-face.
"Sweet summer evenings, hot wine and bread /
Sharing your supper, sharing your bed /
Simple joys have a simple voice:
It says why not go ahead?"