There is an indication. Ivy is constantly pushing Lena into Axel's arms. She publishes photo from his place without telling Lena that she worked with him (her excuse that she "forgot" to tell i hard to believe). Then she pushes her to work with him. And when she was supposed to accompany her she doesn't arrive for a very long time. The fact that she shares facts from Lena's private life with Axel is also telling.
I'm almost certain that Ivy is in league with Axel.
Well maybe no indication was too strong of a position. I was saying all those things you consider evidence
could also be explained by her personality and world view.
She didn't push her into Axel during the first convo about him showing up. She gives her a somewhat reasonable advice to tell him and be upfront and very clear about things. Ignoring or hiding from a person in the same industry in the same town is not gonna work forever. The only other thing she could do is try to get a restraining order or something but I don't know the conditions required to get one personally.
She works with him, but posts the photo for everyone to see. Lena is gonna see it of course, because Ivy is always telling her to check out her accounts to learn from her. It doesn't add up and Ivy even says this. Her argument that having to get cut off from one of the top photographers in the industry because they broke up holds some water, although not by most people's viewpoint of what a BFF should do. Yes, this move was a bit shitty, but given her personality, she might not see it as such. Kinda like Jeremy going for Alison when Ian tells him he wants her to be an exclusive fuckbuddy. One of those things that are in the grey area of brocode.
She tells Lena she could consider Axel's connection to Wildcats. Is it a smart thing to do? Probably not. But I can also interpret as her being very self assured and expecting others to be as such. "Girl, if I was you, I would use his connections to Wildcats to boost my career. What's the problem? You already had the conversation and settled the past issues right? Just don't do anything stupid!" Something like that. Again, not many people would think it's a good idea, but Ivy could.
I can't really remember what facts she shared about Lena with Axel, so I can't comment on this. But I can actually add something to the snake bitch interpretation if this interaction wasn't what you were talking about. When Ian is talking to Ivy at the club, Axel shows up. He says something like "I'd like to buy you a drink, but I believe Ivy and I have something to discuss." And she's like "Uhh... Yea." This could make us question what they discussed. The straightforward answer is about her photoshoot and discussing Wildcats. The shady interpretation would be collusion or even domination. Her "Uhh... Yea" seems surprisingly meek for someone who is usually super confident.
As for me? I think it could go either way, not because the evidence is so damning, but because of Chekhov's gun. I think there is some amount of doubt as you've pointed out, and from a narrative perspective, it needs to pay off. But Chekhov's gun is just one principle of writing and isn't an immutable standard. The fact that we could interpret it both ways means either outcome to this would be an interesting development.
Personally... I thrive on betrayal, cheating, and subversion of character. Lol, it would be so fucking hot if the normally confident and sexually free Ivy was basically under Axel's thumb. I can imagine this would cause quite an uproar if unavoidable though. Perhaps it could be gated by some flags and lena_ivy points.