My boyfriend's sister was supposed to pick Isabelle up at 11 for a birthday party (I can't take her…

My boyfriend's sister was supposed to pick Isabelle up at 11 for a birthday party (I can't take her bc I'm working on school). We literally planned this two weeks ago and she told me this morning she'd be here. It's 1130 and she hasn't shown up, won't answer texts or calls. I hate unreliable people.