She’s scared that your relationship is going to end as brutally as every other relationship in her past did. That, even though this time feels entirely different, it will all end the same — with her in tatters.
She’s scared that she isn’t the relationship type. That, even though she’s been dreaming of marriage since she was a little girl, she doesn’t have what it takes to make love last. That she’s going to screw everything up.
She’s scared that you’ll get bored of her. That you’ll get tired of listening to her stories and eating her cooking and making love to her. That you’ll get hungry for something fresh, something new and exciting.
She’s scared that you’ll wake up one day and decide that you’ve fallen out of love with her. That she did nothing wrong, but you lost feelings for her anyway. That it just happened and there was nothing either of you could have done to stop it.
She’s scared that your I love yous will end up feeling forced instead of authentic. That you’ll kiss her out of obligation and not because she’s the one that you’re choosing. That you’ll start treating time with her like a chore instead of a prize.
She’s scared that you’re not as perfect as you seem. That your ‘good guy’ act will slowly fade away and will be replaced by someone cruel, someone that she doesn’t want to spend eternity with.
She’s scared that you’ll cheat on her. That you’ll eventually find someone younger and pretty that you like better. That you’ll start coming home later and later until you stop coming home at all.
She’s scared that all of the happy memories that you shared will become painful ones. That she won’t be able to look back at her favorite pictures, because you tainted them with absence.
She’s scared that you’ll abandon her after she gives you everything. That she’ll change her entire life path so that she can spend forever with you — and then you’ll leave her behind and turn her world inside out.
She’s scared that she’ll do something small and stupid that will ruin the best thing that’s ever happened to her.
She’s scared that, if you ever decide to walk away, she’ll fall apart without you.
And she’s scared that tomorrow won’t be as wonderful as today — because how could things get any better than perfection? 
