She can't have one rule for herself and a different one for you. So yes, just talk to her and tell her you were really looking forward to your friends coming and it's all planned and sorted, so they ARE coming to stay because it is just as much your flat as hers. If she objects, tell her you don't want her friends there. If she is allowed to tell you that you aren't allowed people over, then you have the same right. Just don't back down.