Huh. A little weird, I guess.
HOWEVER: I can't say I blame someone for doing due diligence, I am impressed that she actually questioned you (some people would have freaked out and said 'forget it'), and provided that she approached it in a "hey, I was just wondering, haha" way; then I wouldn't really mark it as a strike against them.
That said, I agree with playfelt in that it's not really any of her business what you do outside of dayhome hours. If you get a bit of a bad vibe from the face-to-face, after her questioning this matter, then I may begin to tread carefully.
Hope it goes well; and you fill that spot right away with a great family.
And BOOOOOOOO on the family that backed out on you!!