I think she just didn't want to deal with conflict on the phone or feel self-conscious in the middle of all the "fun" having to call the "family" since they are most likely all single and not in a situation like that at all.
It is POSSIBLE that the event in itself was the only thing and she was "guilty" of. And this may have given her additional rationalization that she "shouldn't HAVE to call" since she wasn't doing anything "wrong." But that's silly. I agree, it was inconsiderate at best. I think you have a good feel for the best way to handle it.
Be careful though, when you say, "Did you have a good time?" TRY REALLY HARD not to sound sarcastic. My H worked late one night recently when a tattoo show filmed a pilot episode at his work. He DID call, but I was still peeved that he was home HOURS later than he originally predicted and NEVER said he was sorry, just came in and acted like no big deal, man, what a long day. I said, "Did you have fun?" and he blew up, "NO! I didn't have fun - it was WORK!!" Hmph. Whatever. lol!
