Florence - the daughter you never knew the Donahue's had

According to the notes I have, the Donahue's have a daughter named Florence. The notes don't say how old she is but I'd reckon she must be 19 or 20 and probably married - and probably moved away.  Otherwise, we would have heard about her.  Rush certainly would have mentioned her if she was his age.  And if she was a little girl, she'd be out and about, which she never is.