This is so interesting to me. Our S recently got engaged after dating 5+ years. At the time, he had met only her aunt and not her mom nor her sibs. She had met us several times and some of our relatives but not D, even though they were in same city as D several times. They were both finally in HI and she and D finally met and she met the extended family and attended a wedding of my nephew S’s cousin who lived in DC with his fiancée.
S finally did meet more of fiancée’s family when he attended a wedding near where fiancée was raised. Fiancée’s mom and sibs and we still have not met and currently we don’t have plans to meet prior to the wedding, whenever that will be in Honolulu.
I agree it would be good to ask your S to ask GF having you guys meet her folks at graduation is something she/they would like or perhaps if there is a less hectic time/place to meet.