The first choice is when she sends you the pic. You can tell him you think she is hot which is the most affirming choice. You didn't tell him at that time to give you dibs on her. Plus, Alison was sending pics to Jeremy also. She clearly has some weird obsession with Ian, probably since their high school days. She will interrupt Ian's conversations with other characters to talk to him lol. Her character is quite interesting. She doesn't want a serious relationship, except secretly with Ian, but since Ian has Lena, she is kinda using Jeremy as a consolation prize or to invoke jealousy. However, neither Ian or Jeremy knows this yet. For them, shes just looking for casual hook ups after her break up and the mood was "may the best man win."
I looked through the script for the "block jeremy" choice because I have not played that route. Jeremy's reasoning isn't wrong really, but I can see how that might not be the most bro move on his part. You could argue Ian scored first and "won" the free for all, so Jeremy should back off. But it's also true that Alison isn't Ian's girlfriend, and that Ian is being insecure and selfish to try and monopolize a fuck buddy. He says in multiple instances girlfriends are where he draws the line (although lets hope that cheating Lena can seduce him with powers of the MC).
I can see why this might annoy people though. Neither in real life, or in most male MC games, do we (average people) see this kinda free for all fuck buddy parade between friends. It's an unfamiliar situation for me and I assume most other people. For people who hate sharing of any form, a character like Jeremy would understandably not get the benefit of doubt when it comes to his character.
