Annoyed, what should I do about this friend?

So my friend asked me to lunch tomorrow. When she asked she didn't have a place or time picked out and said she'd get back to me. Well I texted her at 9 pm and was like I need a time and place. Well then her granddaughter texted at 11 pm and asked if her and her friend could go to lunch with us. Then asked me where and a good time. Should I cancel plans with her? I kinda feel like she should have asked me or told her granddaughter yes or no. She put me on the spot