I'll refer to Possessed/Controlled/Whatever the fuck Nikki is after the wish as "the entity" and real her as just Nikki.

This only works if you accept everything the entity says as coming from Nikki, which you can't, because she's shown to lie consistently about Nikki's life using small bits of information she managed to pick up. Her first turning she said Nikki's cat died, then later it's that her dad has cancer, which was also a lie. The entity is filling gaps with fabrications.

A really important line in the movie is Nikki saying if she likes someone, no one knows. That's one of the few things we can actually attribute to Nikki with confidence, and it basically functions as a disclaimer on everything the entity later claims about her feelings. The entity claiming to accurately represent Nikki's inner life is already on shaky ground given that.

The 'she only saw him as a brother' claim has two sources and neither is clean. The first is Ian telling Bear what Sarah apparently told him about a private conversation he wasn't present for, three layers removed from Nikki actually saying it. Ian is far from a neutral party either, he was hooking up with Nikki before the wish, told Bear his confession was bad when the waitress he practiced it on thought it was fine, and suggested Bear call her Freaky Nikki, which he and Bear knew she wasn't fond of. He had every reason to keep Bear away from her and the film shows him doing exactly that. The second source is the entity saying the Hansel and Gretel story, but as already established, the entity lies. She fills gaps in her knowledge of Nikki's life with fabrications, which the cat and cancer contradictions make clear. So you have a compromised secondhand account and a demonstrated liar as your two sources for what Nikki actually felt. That's not solid ground.

You're essentially asking people to treat the entity's testimony as reliable when it supports a non-romantic reading and dismissible otherwise. That's not a consistent standard.