No, she refers to herself as being not human multiple times.
She doesn't directly says she is not-human at all during
Mystic Square, the only instance she says something close to "Im-not-human" is during Reimu's Main Scenario and Marisa's Extra Scenario:
To Reimu: "A human like you coming here probably means that you're prepared to to face us!!"
To Marisa: "This is magic that a human like you would never be able to master."
But even this is not a concrete evidence of Alice being not-human, after all she could just be emphasizing her superiority over
simple humans (because she obtained a power superior to what a human can achieve?). And, even if she refers to Reimu and Marisa as "humans" that doesn't means she is not human; a lot of characters do the same, like Mokou during Imperishable Night to the Barrier Team and the Magic Team:
To Barrier Team: "To think that there'd be humans wandering around in here."
To Magic Team: "Oh, since when have humans been this foolish?"
And as we all know, Mokou is a human being; a human being who attained a power beyond a mere human, but is still a human.
Ergo, a character refering to others as
humans doesn't mean he/she is not human himself/herself.
And I only pull out the unreliability thing in regards to Alice because game-canon says the exact opposite of what she claims. Especially since PCB outright states that Mystic Square IS canon because Alice remembers Reimu [While Reimu has forgotten her or doesn't recognize her due to the redesign]; meaning Akyu is incorrect about Alice being 'human' at any point.
Why you say Alice being a human at any point is false?
AFAIK a human magician
can become a youkai magician after long exposure to high amount of magic. For example Byakuren; she was a normal (human) nun, but after her brother's death she began to practice black magic and became a youkai magician due to this. So Alice could have perfectly been a human at the beginning but became a youkai after learning the Grimoire of Alice's Magic or whatever magic she found.