It's just the way she is. Like, I despise hugs. In my head, when someone hugs me, all I can think is "oh no oh no uggggggggg when will this be OVER?"
it's how she feels comfortable. She might warm up someday, or she may always cringe and clam up when you try holding her.
Is she butch? Cause I know most butches are phobic about people touching them, sexually or just in general.
It doesn't mean she doesn't love/like you. She can love you with all her heart and not feel comfortable with being held like that. It's just the way she is.
She might be self conscious about letting you do things to her.