You tell her to pray 'Istikhara' and wait. If it is a good marriage, she will feel good about it and approve it for herself. If she is against it, totally, she can tell them that she isn't ready for marriage and it isn't her time yet. She should disregard her brothers comments, because in the future they will not be there when she cries for help. The father will get mad, upset - who cares, he'll get over it.

And 27 isn't old!