My first thought as I was reading was the same as yours, I would be very hurt and a little upset that DD was basically ignored on such a big occasion.
As I was reading though, I did have a thought, and I may be way off mark (and I have been many times

), but here goes...
Did you have a graduation "party" for DD? Around here, most people have a gathering at their home, a park or church to honor the Graduate. An invitation is sent out, not exactly to the graduation ceremony, but to the party.
If you didn't send out an announcement to anyone, could they maybe be thinking that you
did have a party and they just weren't invited? I am just trying to think of a reason from the other side why they didn't acknowledge your DD. Could they have been hurt and felt a little slighted that they weren't invited to her party (even if you didn't have one).
Could you have a Fall gathering maybe? Print out your own invitations and plan it on a weekend when DD will be home from college. Have them read something like "In celebration of _______, we are having a gathering to honor her graduation from HS"
I am not suggesting this for the presents, but more for your DD to have a chance to see these people and let them know how proud they are of her and all she has accomplished.
My DH's niece graduated HS in June, she knew we couldn't come to the graduation since last January because my DH had a conference for work. We never heard anything from her, and we were a little hurt and I thought maybe she never sent an announcement because she knew we couldn't come. I still would have liked an announcement though, with a senior picture at least. When we got back from our trip, there still was nothing from her... so I sent a card with a check and told her we were sorry we missed her big day. Later I found out no one in the family got any announcement, they were just told the info by phone so they could attend. So, we were feeling slighted for no reason. (Still waiting for the thank-you, but since she has never sent them for birthday or Christmas gifts either, I'm not holding my breath.)