Should I add her ?

Hi, so I met this girl in the gym this evening.

When I worked out she looked at me pretty often so I also kept looking at her, she smiled. For me, those were signals that she might like me.

~10 min later when she was walking to the locker room and I followed her and before she opened the door to the women's locker room the conversation went as it follows :

Me : "Hey wait"
She turns around, smiles : "yea?" Me : "Can I ask you a question?"
She : "Sure"
Me : "Do you have a boyfriend?"
She: (smiles) "No"
Me : "May I invite you to go eat something?" (It may sound kinda dumb in english, I actually am german and asked her in a polite way)
She : "Of course!" (smiles)
Me : (about to ask her for her number)
She : "Wanna give me your number ?"
Me : (Giving out my number, I also saw that she was seriously typing me in as a contact) " She : "Okay I'll text you" (smiles)

Then we both went in our locker rooms and back home later (didn't see each other after that). So now I am waiting for her to text me via whatsapp pretty much. I hit the gym at like ~6pm and now its 9pm, of course it takes time.

Now to my question : By randomly searching her first name in facebook I found her. Should I add her ? Or wait for her to text me first ? Sorry If my post may sound stupid, I'm just kinda excited that it went so well (1st time asking out a girl out of the blue)