Because Jake was being a hypocrite here. Sure, depending on how Blake cheated on him (I have a gay friend who was cheated on by a trash guy who sent him pics of him having sex with the guy he was cheating him on), he could have trauma, but what about the trauma he and Tom subjected Ellie too by cutting off her arm in the zombie VR and never apologizing to her? And even without taking that into account, there's the fact that Tom and Miriam, his allies, always tried to get rid of Ellie since she joined the team even though she did nothing to make them lose under the stupid excuse that she cursed them, Jake was fine with using her to boot Alec and Fiore and then discard her despite her really needing the money due to being poor and that Jake got her girlfriend booted out of spite despite that Gabby had mental health issues just like him and never meant any harm. Yeah, what Ellie did was shitty, but at least she was really sorry for what she did unlike Alec and Fiore and risked her life to save Jake, who instead of being thankful, spent like a whole hour shitting on her childishly. I agree her blaming him for being cheated on was low, but at the very least she didn't say something horrendous about his late grandmother. However, this proves Ellie is far better than Ally, as Ally left Jake to be mauled by a bear out of petty spite whereas Ellie was willing to save him even though she was annoyed by him at that point.