You have the answer then; she's not on nearly enough thyroxine yet. I would be a wreck with a Tsh of thar level.
Another 25 or better still 50 should help a lot.
Tsh needs to be ideally around or just below 1.
You need to fully understand how thyroid function and disease works. This is a BMA book outlining the basics (and medications that affect thyroxine) and worth getting for the basic ins and outs of the disease, and linked diseases such as coeliac and pernicious anaemia. I wouldn't make huge changes to diet till thyroid levels are stabilised and she's still not well. Do it step by step.
www.amazon.co.uk/Thyroid-Disorders-Understanding-Family-Doctor/dp/1903474191
Selenium is really important for conversion from t4 to the active useable form, t3. So try to eat a Brazil nut a day but ideally find a multivitamin with selenium in.
Iodine is really important for thyroid health; not so crucial if you're on thyroxine ironically but still worth including. Too much is bad too. She either needs more dairy alongside her white fish or again a multivitamin.
Iron is also really important (again more so for a healthy thyroid function, but still very important for one that's not working). It's worth finding out what her ferritin levels are (stored iron) as hypothyroidism causes anaemia and you need the iron to feel better.
As said above, calcium and magnesium and vitamin d are also really important. If she was ill last summer her vitamin d may be low.
Do you know if all / any these things were also tested? Could you get printouts of blood tests from over the last year? If so post here.
It may be worth letting college aware of this; she really is quite ill. Unless you've experienced it it's really hard to explain it understand how you feel. Your cognition is great affected too. It's like automatic iq reduction. Muscles become very weak as well; I lost a lot of muscle mass when I was diagnosed and any big subsequent blips.
As a starting point you could give her the basic boots a-z multivitamin with minerals, but there are better ones with more b vitamins - I'll have to look later. Good selenium and iodine content, but if she's low in ferritin, iron, vit d and b12, she will need more.
http://www.boots.com/boots-a-z-complete-vitamins-and-minerals-180-tablets-10149657?cmmmc=bmmmGoogle+Boots+PLAsAs--BAU---C=%28GB%3AWhoop%21%29+Boots+Shopping+-+Category+-+Health+and+Pharmacy+-+Mobile%28GB%3AWhoop%21%29+Boots+Pharmaceuticals&gclid=EAIaIQobChMIs6me032AIVg7ftCh3IuAkZEAQYASABEgK4ffDBwE&gclsrc=aw.ds
Ps I have a relative who is a researcher in the field, who has given me much info, and have been on thyroxine for 20 years.
The British Thyroid Foundation are an excellent charity and have resources particular to young people and children with the disease. Also Helplines you can call.