My daughter is 13, and she is always complaining about having head aches allot. She dosnt drink allot of water though, could that be the cause?

Headaches. Headaches could be coming from tension, eye strain, tooth grinding, dehydration, lack of sleep/poor sleep, skipping meals, stress, sleep apnea/snoring, or chronic sinus problems.
Yes but... Dehydration can cause headaches, as can a number of other things. In all these cases the best thing is to see the pediatrician to make sure there is no other more serious cause.
? risk migraine. About 20% of all girls will develop migraine and most start to show signs as they enter puberty. This should be discussed with her primary doctor.