It is really sad, but you know that I've noticed Sasha being really lazy and weeing in the house a few times since she's be in season, it might be something to do with that.
Sasha has also had a few accidents upstairs too, I think she gets really excited because she's managed to get up there, the safety gate is usually locked at the bottom, but now and again someone leaves it open and she darts up there.
As to the nighttime wees, we've always put Sasha in her huge crate at night and when we leave the house in the day too, she has never had any wees or anything else in it, but she is dying to go outside when we come home/wake up . Maybe you could try a crate?
It's so funny, Sasha absolutely hates the rain and water of any kind, you'd laugh if you saw me standing in our tiny back garden holding an umbrella with the rain hammering down, it's as if she thinks I'll only go out there if you come with me!
I hope the long chain helps and maybe the operation will make her not want to go walk-about so much, it's amazing that she hasn't found a handsome male dog and isn't expecting after all her expeditions .
Oh, are you on facebook by the way?