Well, he's not her significant other yet...but yea, she's leading him on this way. There is still some leeway if she confesses the truth before they get together...but a lie is a lie.
Plot twist: He's seen her at a fan event or panel and is aware that she's his fan, but he likes her so much that he pretends to go along with her lie, just to keep hanging out with her but ends up going too deep into his own lie about him not knowing that she's lying.
Lie-ception.