Alison will offer Ian to come with her to her place to "talk about Gillian" afterwards. If Ian takes her up on this offer she'll hit on him.
Note: this won't happen if Ian/Alison broke up. Which might actually be a bug.
PilotLara maybe this is worth looking at? In Ch.11 on Ian's side:
Python:
if ian_alison_breakup:
// ...
else:
// ...
else: # Never had sex or stopped hooking up (Emma path / broke up)
a "Hey, about earlier... I understood you not wanting to talk about Gillian at that moment, but if you need to get anything off your chest, I'm here to listen."
// ...
The wording in the comment suggests that Alison would also make her "friendly" offer if she and Ian broke up, however this won't happen because it's in a branch that depends on
ian_alison_breakup
being
false
. I'd guess only EK would really know what they had on mind here.