Don gave Betsy a gift that she simply tosses to the side, after a mediocre comment 'it's beautiful', or something like that.  I didn't get WHY she had this reaction....can anyone tell me ?

Her comment was "Now I'll have something beautiful to look at when I'm telling stories about the time I was in Rome".  She's upset because Don is gone a lot and she's left alone in her unsatisfying life. She came back from this wonderful trip, where she was useful (knowing the language) and respected. And now she's back home with the same problems, the same snide friend making comments, Don will be gone again soon.

So she'll 'have something to look at' because Don won't be there.

Kitkat-

That’s’ a good take.  I would only add one more thought and maybe it’s a stretch.  The gift was a gold necklace of the coliseum.  They never made it to the coliseum. 

It was right there just within reach of seeing it and experience it but Don’s schedule didn’t allow that to become a reality.  Instead of taking in the sites of Rome they played fun (sexy) role playing games pretending to be people they are not.