What would you do (if anything)?

[luvdzny]

Shouldn't the fact that we've received invitations for every possible activity

I think that may be the difference, you have given gifts when your received an invitation for an event, these people did not receive an invitiation so maybe that is why they did not send a gift.

It sounds like you raised a wonderful daughter and you should be proud!

 

[EthansMom]

I agree with what some of the other posters have said. In my family, you usually receive gifts at a graduation party held after graduation. It may be that your in-laws are/were waiting for an invitation to a graduation party.