They have a fund to help new parents in need of financial support such as travelling to hospitals when preemie babies are having prolonged treatment, hence the decision to start asking members to pay to join. A great organisation, though, and the discount offers they give cover the joining fee after a short time.
Why don't you join TAMBA (Twins And Multiple Births Association) with her? They do online magazine-type newsletters and emais, have a great website that will provide all the contacts, tips, articles and offers that you can use with twins in the family.