There’s two ways this can go: (1) either she’s been there, done that, or (2) she’s never had someone like you before and thinks this is too good to be true.
It might be something all too familiar to her. Love, and left. That’s what she was and what she thinks she still is.
She is so used to this pattern of destruction that she believes its only a matter of time that everything will go wrong the minute anything becomes so right. What goes up, must come down, and whenever her life falls, it comes back lower than where she started.
She’s scared you’re going to leave because she’s even more terrified of the way she’ll feel if when you do. She knows it will be messy — and that’s an understatement.
Love her in a way that makes her feel cared for. That’s makes her believe that even if things go wrong, you’ll find a way to make them right. That not everything is all perfect sunshine and roses, but she’ll be in your arms when they’re not.
Love her and make her know that you’re there. When she needs you, you’re there to listen to her. That she can speak her thoughts without being judged. That you’ll not always understand, but will definitely try.
Or, she’s scared you’re going to leave because more often than not, her insecurities surround her like a life-consuming black cloud — that whispers things she thinks are true, and causes her to act in ways she never would. Her insecurities win the space in her head where happiness once grew and they take over. Letting her believe she’s not enough, that you’ll leave her for someone else eventually, someone who’s better for you, someone who’s better than her.
Love her in a way that accepts her insecurities. Don’t ever try to take them away, instead, try to quiet them down. Accept that sometimes, she will say things she doesn’t mean, or do things she wouldn’t ever intend to. Love her until she makes her insecurities fade away herself.
Love her and make her know that’s she’s enough. Say it again and again, and make her feel special everyday. Little things count. Let her know that she can’t be the only thing that matters to you, but she’s definitely at the top part of that important list. Love her in a way that shows how much she means to you.
Love her in a way that assures her that the only place you plan to be is by her side.