Welcome to the Nexus!
Ultimately the choice is between you and your daughter, but here's what I think:
First off, I don't think she is too young to start experimenting with psychedelics, I started at the same age. If she wants to start experimenting with DMT, I would suggest to brew
Ayahuasca. However, if she wants to smoke DMT I don't think it's a problem at all, but considering it's her first time with psychedelics, the learning curve will be a lot easier. It's good that she has been researching this stuff for a while, that matters a lot, since she knows what she is doing and what she should expect -- i.e., this is a safe experience for people who are stable and who do not have a history of mental disease. Erowid is a good source for all drugs in general, but always take any one source with a grain of salt. Wikipedia has good information on DMT as well as the Wiki on this site and the whole site in general. I believe that if she has been honestly researching this for a while now, then she knows what she is talking about and most importantly she knows what she is getting into.
HOWEVER: This is an extremely powerful experience, whether you are 17 or in your fifties. So if you think that your daughter is not stable, doing this on a whim, not mature, or weakly spirited, I do not recommend this at all for her. You definitely need to be a strong individual to handle this.
If you want to read about clinical trials, there is a great book called DMT: The Spirit Molecule by Dr. Rick Strassman. Strassman was a researcher that experimented with DMT on human volunteers. The LD50 for DMT is high, and it's not toxic to the body when used appropriately.
Since you are taking your time to find out more about this substance instead of just shutting her out I get the feeling that you are at least open to the idea. I wish you and especially your daughter the best of luck.