I think there may be a misunderstanding of what GMRS is for - it's for any kind of conversation, not just intra-family communication. The two operators having a discussion had just as much right to be talking on that frequency as your family. Now, if your wife had emergency traffic, that's a completely different situation, but otherwise it's first come-first served. It would have been considerate to allow your wife to break in, but not obligatory. There is no requirement to limit the duration of a conversation on GMRS, only that a station must identify every 15 minutes.
Wow.