Hitler started out that way too. Early on, his approach to women was being vaguely nearby on some occasions, not speaking to them, and wonder why she didn't respond to his non-communication
She's saying these things to him to reinforce it into his subconscious. One day he may start believing those lies, and one day they may actually come true. Except the tall thing, he's fucked.
No gf saying it of course, but my daily affirmations for the last 20 years are: "you're a piece of shit. You're worthless. You're single because you're worthless. Don't seek a gf, no one deserves to suffer your existence. Blue collar shit work is the only thing you're capable of. You have decayed dog shit where your memory should be. Get fucked asshole, I hate you."
It's nearly impossible to stop because I honestly not only believe it, but it's completely true. It's not something that can be denied. It's a fun life.
Homie has his girl become his hype man that's the best thing that could happen and he's still questioning it. I feel for this guy and his overanalyzing brain.
Stop. Shut up. Don't question it - you can't apply logic to this. Just enjoy it while it lasts. If it's Kris happening over a prolonged period, them she's a keeper.
What she's doing is called "affection." It can come in different forms, usually from family, friends, and romantic partners. If you're like most guys, you probably didn't experience much of it before. If that's true, you wouldn't know what it is. I advise therapy, because you don't know what you don't know.