Attempting to do a century ride on only one ride/week? I don't understand why she would undertake such a lofty goal on such minimal training. It won't be fun for her or her ride partners.

Yes, it's important to make sacrifices for friends, but that goes both ways. What sacrifices is she making to accommodate your needs? Riding just once/week and then expecting friends to plod along for 100 miles isn't really fair, either. Why doesn't she shoot for a half century or metric, instead? Even that will be painful, but not nearly as much so as a full century.