A girl gave me her number today, when do I text her?

Before I explain, she has a boyfriend. But she was flirting with me for a while then she backed off now she's friendly wih me again. I'm scared of her. And she probably knows I'm really shy already. So today in cl she said you have a phone right? Then she said did I want her number, and I said yes then she said let me see your phone then she put her number in. Do I text her today or will it matter since she has a boyfriend?