Need alarm clock for DD who just doesn't hear it

I have an alarm clock on my phone that makes me do math problems to dismiss it. You say she doesn't hear it though, so it might not work.

This won't be a popular opinion, and I am certainly not telling you what to do, but perhaps she will "hear" it better if she missed out on something important as a result of not hearing her clock. That certainly has worked for me. Worry that I will be late for work somehow helps me hear that thing better.

Oh, I used to have one of those "big ben" alarm clocks. That thing was so loud it would wake the dead. I also kept it across the room so I had to get up to turn it off.

Search Amazon for "super loud alarm clock". The search came up with lots of options. I don't know which one would work for you so I didn't want to just choose a link especially since there are so many listed.

Oh, and start sending those heavy sleepers to bed earlier. Every time they hit snooze sent them to bed thrity minutes earlier the next night until they are getting enough sleep they aren't in a deep sleep stage at wake up time. Yeah, it may mean they are going to bed a 6 pm!

I just thought of something else. Are you sure she isn't up off and on throughout the night texting or checking social networking? When I was doing pediatrics I used to see teens texting and social networking periodically all night long. It seemed they never really fell into a deep sleep because they would check their phone every time they woke up and would respond to any texts. So, lets say normally you would wake up, turn over, look at the clock, fall back to sleep immediately. They would wake up, check their phone, respond to texts, maybe check facebook, and then fall back to sleep. But I wonder how much deep sleep they were getting. All that "blue light" and stimulation from technology can really impact sleep. So I can imagine it would be much harder to wake up in the morning.

Loud - very loud.

I've long said that I'd do best with an alarm clock that picked up the bed and dumped me out.
Having said that, I also do the trick of leaving my phone across the room.

I had one for a long time that played reveille.

Someone mentioned a 120dB alarm?  

For someone with normal hearing, that's in the range of acoustic trauma and could cause noise-induced hearing loss. The longer you let the alarm sound, the worse the damage.

Decibel increases aren't incremental. They're like earthquakes. A 120 dB sound is ten times louder than a 110dB sound.

(Your audiology lesson for the day. )