My girlfriend has been getting heaps of bad headaches/migraines and has been getting very tired recently. She recently managed to just go home after school and sleep for a straight 15 hours and still be tired the next day. She is getting migraines a lot more and im getting really worried.

I have a few ideas that may be causing this.
For one she drinks a LOT of water...like im talking about up to 10 litres a day. She used to do a lot of training for sport and she was drinking a lot of water which is good, but now that she's stop all the working out, she is still drinking just as much water.

Ive read that drinking to much water can wash out ur electrolytes, which could be causing how tired she is. And that drink too much water can dilute the blood and the cells drain water from the blood and cause them to swell, and this can cause the brain to swell and cause headaches. This is just things ive been reading, but i think im overreacting, so i need someone else's opinion.