I think the 'Maet' in my above post is supposed to be 'Mary', FWIW.
I've come up with some marriage items for Dorothy's siblings, and names of a few of their descendents, but I don't have my notes on this computer. I can post what I can remember off the top of my head if anyone is interested.
ETA: I also have come up with an idea to maybe get the police files, if they can be had. I'll post how it turns out, one way or the other.
I sent an email to the NY Times, and made, IMO, a very compelling case for them to petition LE to release the files on Dorothy, and to write a story on this to come out on the 100th anniversary of Dorothy being reported missing to the media and public. I never heard back from them, and it does't appear they went for it.
I'll do details when I have more time, but in a nutshell, I found Dorothy's coming out party, and several references of her attending other's parties. I found engagements and marriages of her siblings, births of their children, and deaths for most of her family. I even found births of siblings grandchildren, but no sign of Dorothy. I also found several trips to Europe by the family for the year of 1911, which had me at first leaning towards Dorothy having gone off to Europe and her family finding her and knowing where she was. I could even believe the family would continue the pretense of searching for her to avoid scandal, but it's hard for me to believe she was just sitting around in Europe as her family went on with their lives, especially after the death of her father.
I plan on researching how often family members went to Europe after 1911. Off the top of my head, the mother went with the brother right after Dorothy went missing, and stayed a week longer than the brother did. I also show the mother coming back from Europe in June, seemingly with no other family, just in time to make the wedding of I believe the younger brother. I then found the father, mother, and sister go back to Europe in August, and stay until towards the end of October. I can't decide if I think they were going to visit Dorothy, or going to escape NY, and the media attention. It just seems to me to be a LOT of trips to Europe right after Dorothy goes missing, especially considering it was at least a week one-way trip, though I guess being on maybe a luxury liner would not make it so bad a trip.