(The grandmothers) have texted, thanking us for coming and for the nice gifts. How do I respond? It feels misplaced to say ...

Miss Manners would have you text back that you are “Glad they are enjoying the gift.” This will reassure the sisters-in-law that you have no quarrel with them -- while its brevity relieves you of ...

I suspect that we’re not to expect a reply from the recipient, as the text went into detail how appreciative the graduate is.