Wait times to clear customs in SFO vary from 17 minutes to 90 minutes depending on time of day. Since she is an arriving K1 she will likely be directed to secondary inspection which will significantly add time to her ability to get through the immigration process. Then she must collect her baggage, clear customs, recheck her bags, change terminals, clear security again, find her gate. Not a recipe for success in an hours time. That's why i always try to have my last stop in my itinerary be my first stop in country and therefore my POE.