Meet Me Under the Mistletoe by Danielle Baker

Noelle
All she wants is a quiet, chill Christmas Eve with the family.
Instead, Noelle Compton has been thrust headfirst into planning and organizing a secret proposal for her sister. And to make matters worse, she forgot the mistletoe, the key component to Beau’s romantic Christmas Eve proposal.
When her best friend Theo comes in wearing a full Santa suit, bearing the forgotten mistletoe, Noelle could kiss him.

Theo
Only he doesn’t want to stop with one chaste peck on the cheek in thanks.
Oh no, Theo Collins wants much, much more from Noelle.
He’s waited years for this moment, and he isn’t going to let it pass him by, not when he’s finally got her where he wants her–under the mistletoe at last.
So when she teases him and asks him what he wants for Christmas, his only answer… is her.