Rather than texting her, you should send her a card - the old style paper card and not an e-card.
It should be very simple card, without any lovey dovey stuff on it. A simple plain card with something like "Happy Birthday etc". Just something that suggests well wishes for her. If you have never sent her card except for on Valentine's day - it will be a good surprise for her and something hand written makes it personal.
Whatever you write - make sure there is no love dovey feelings implied or otherwise.
You want to get to know her as a friend all over again. Don't rush into things and be strong.
Hope things work out for you