“If Harry was a girl…”
“…then Snape would be a creep.”
Or worse: “a pedophile”. This, assuming that female Harry would look almost exactly like her mother Lily Evans.
First, the reader should know that, unlike his detractors proclaim, Snape was not obsessed with Lily (see: Love, not desire!), so there’s no reason he would be obsessed with a Lily look-alike.
Second, this is Snape’s reaction to being reminded of Lily:
“Her son lives. He has her eyes, precisely her eyes. You remember the shape and color of Lily Evans’s eyes, I am sure?”
“DON’T!” bellowed Snape. “Gone . . . dead . . .”
“Is this remorse, Severus?”
“I wish . . . I wish I were dead. . . .”
Huh. So Snape’s first and visceral reaction is pain. Pain enough that he asks Dumbledore to stop reminding him of Lily’s features (and her death). Pain enough that he wishes to die.
Implying that every time he looked at Harry in the eyes, it must have been quite painful (and not just because Harry was James 2.0).
Considering this, how painful do you think it would have been to see a carbon-copy of Lily in female Harry? Hard to imagine he would get a boner under these circumstances. I’d rather think he would try to avoid her presence as much as possible.
Three, there is not a single recount of Snape being a creep to students. In particular, there is no recount of him being particularly weird around Ginny Weasley, a red-headed girl that Harry will marry. Talk about an Oedipus complex.

(Is it canon that Ginny’s red hair color is that different from Lily’s? She sure isn’t blonde like in this picture.)
“But Ginny and Lily are different!” And so would female Harry be. If you can argue that Harry has not, in fact, lusted for his mother, despite…
His eyes feasted on her, and he thought that he would like to stand and look at her forever, and that would be enough.
…then you can see how absurd it is to claim Snape would be a creep around female Harry.
Case closed.