I live very close to this area and hike there frequently, so I went out yesterday afternoon and searched. There was a helicopter out there searching for many hours along with many members of the public. My friends and I searched a couple of trails on Northern side of the peak. It wasn't the area she was supposed to go, but we reasoned that maybe she took a wrong turn on the way down.
So, to explain a bit, she was part of a group called "Build a School Foundation." They were doing a 5K walk on the mountain. They charged $20 per person and were raising money for schools to be built in SE Asia including Vietnam. It appears that most attending the group walk were Vietnamese-American. Most of the people were wearing the black T-shirt with the heart on it, including the missing woman.
A lot of information in the press release is inaccurate, and they haven't bothered to correct it. The group set off at 8AM. By 9:30 or so, she is seen on a livestream video at the top of the mountain. You can find it by searching for a Facebook group "Find Dina Diem Le Nguyen of San Diego 6/23/2004". She is in the background of the video several times, along with about 30 other people from the group. It seems to be a very lively group with people and everyone seems to be in good spirits, greeting each other, chatting, and taking photos. Another woman (who has already identified herself and has no further information) takes the missing woman's photo during the livestream. Then Dina DIem wanders off to the fenced area surrounding the radio towers. My speculation is that she was standing there to get a little shade. She is near others but doesn't appear to be talking to them. Then she walks away from the camera into the distance. She doesn't seem to be conversing with anyone else.
Supposedly she contacted her sister at 10:08 AM stating that she was hot and tired. I don't know if the sister was also part of the walk, or at home, or what. That is the last contact with her.
She was dressed inappropriately for the 90 degree weather. She was wearing a long sleeved purple shirt with the black T shirt over it, along with long black pants. She was also carrying a backpack.
These trails range from wide fire roads to single track trails. It is nearly impossible to go off the trail, even if you try, due to the thickness of the bushes on both sides of the trails. It would be hard to go more than 10 feet or so even crawling through the bushes. There are multiple branching trails but it is hard to believe they haven't all been searched by this point. They were also going to be using helicopters with thermal sensing overnight.
No updates yet this AM. A search party of people from the walking group was going to be meeting at 5AM. I'm guessing a lot of others will be searching as well.