What should she do?

ok, my friend Sue is going over to my friend Robin’s fiance Harry’s house and they are talking nonstop from 3 in the afternoon to 2 in the morning and Harry doesn’t talk to Robin that long and then Harry and Sue won’t tell Robin what they are talking about together, and Sue won’t take Robin to see him, and yet Sue goes to see him without Robin.. What should Robin do? should she talk to them about it or break up with Harry?