Talking about future plans

Gemma: Hi Cristina! What are you doing on Thursday evening? Are you free?
Cristina: No, I'm not. I'm busy
Gemma: What are you doing?
Cristina: I'm going to shopping with Carla. Do you want to come?
Gemma: Yes, thanks. Is a good idea.
Cristina: Ok. At 7 o'clock in my house.
Gemma: Bye!