Normalising could be one part, equally it could be a guilt reflex as in a 'you are doing OK and are friendly therefore she didn't do anything wrong because it worked out best for everyone' kind of thing.
There is no way to know, I guess as much as anything it just shows that we need to ignore the why's of their behaviour and focus on our reactions.
How's things otherwise?
Both mid 30s, 2 young kids BD 7sep14 XW moved on long ago, now living with OM1 D paperwork in progress