Not likely to work -

As I had mentioned, there are just too many things working against any progress; I am already very well situated in life and happy; the fact that the adoptive parents live too much out of the way (we lived a few houses apart years ago - now ~ 45 miles) and showing up often now after visiting only a few times a year would seem suspicious; their momentary distraction of the ailing mother gave them little time to visit yesterday evening; normally we spend hours together and there would be little chance (and dangerous at that) to try to further any relationship with the girl.
I never sought her out and spent any time with her when she was younger and unpleasant. I think my friends would notice any great shift in my attentions.
I think she might want something she doesn't understand yet but I am reluctant to try developing any closer ties.