I agree, the book mcaimless mentions is a very valuable resource/learning tool when starting out.
Unfortunately Hashimoto's causes a heap of symptoms, but a lot of them are due to other areas of the body going a bit 'off'. A lot of these issues are all interlinked and sadly a lot of doctors only focus on the thyroid and not other area of the body which need looking into too.
Thyroid issues and the auto immune issues don't affect everybody equally, but individually. In my case i'm never extremely cold, but am warm most of the time, i get tired, my hair sheds, but i dont put on weight the way a lot of other hypo sufferers do. I do have menstrual issues which are being sorted by my naturopath and my thyroid doctor. My menstural cycles were once regular and ended up all over the place and got very heavy. Now they are normal and regular with the help of a liquid herbal mixture. This is linked in with the thyroid issues due to other hormones stuffing up along with the thyroid hormones. Most often it's excess estrogen, deficiency in progesterone and higher levels of testosterone. Once the thyroid is addressed with the correct meds, the testosterone most often self corrects on it's own, so long as the doctor is checking that the adrenals are making sufficient of the hormone 'cortisol' and you also have adequate Vitamin D, which is in turn very important for the adrenals....... Can you see now how complex it all is????
The excess estrogen is a little more difficult to treat and not a lot of doctors are interested in correcting hormones. They prefer to stick someone onto birth control pills or do other invasive procedures via a gyn. Me personally, aside from the naturopath's herbs, i've been taking something called "DIM" (it has a much longer name but you can find info on the net via the term DIM). It's been useful in lowering excess estrogen.
If you do research on excess estrogen you will find hypothyroid and adrenal fatigue listed as symptoms and also fibromyalgia (sp?). Why does estrogen get out of balance in the first place.... obviously due to whatever is going on with the thyroid and/or adrenals, but also due to improper phase 2 liver detox, which is supposed to get rid of excess estrogen, but due to being bogged down by bad diet, life style, low iron levels, illness etc it can't achieve it's job correctly. Also a healthy body can metabolise bad excess estrogen into good estrogens which the body can use up, but this isn't going to happen with all the other things going wrong in the body.
The other thing which a lot of people don't realise is the need for good amounts of protein at breakfast to help boost the metabolic rate. You also need excellent levels for your ferritin, Vitamin D, B12, Zinc, Vitamin A, Iodine, magnesium, potassium etc etc. Your daughter ought to have at least ferritin, Vit D and B12 checked out and they ought to be up at the higher end of the lab range.
A lot of people are low in these things due to either gluten intolerance and/or malabsorption of nutrients due to insufficient stomach acids and digestive enzymes. I have this issue with my pancreas as it doesnt produce sufficient enzymes to digest protein foods. The pancreas is part of the whole endocrine system. These lead to malabsorption of nutrients which then affect other systems and how they run.
If your daughter is able to see a naturopath to help settle her periods it would be much faster than a doctor bumbling his/her way around the situation, unless she knows a VERY good doctor. She ought to also get blood tests to check her vitamin/mineral levels, but a urine test is best for iodine chekup as it's more accurate than a blood test.
A saliva hormone test is best for hormones and adrenal checkup, but not a lot of doctors like doing those. Still, a saliva test to check her cortisol levels throughout the day would be advisable so she'll know what's going on with her adrenals throughout an entire day.
Unfortunately with this type of illness and all the symptoms you really have to get pro-active about your own health and not simply leave it up to a doctor to handle. Not many doctors will cover all bases so you can't simply "assume" that your doctor is doing so. You need to do a heap of reasearch and ask a lot of questions. It took me 9 years to get diagnosed and find a good doctor and even so it's difficult sometimes, but at least i know i've got a good foundation in having a good doctor.
Hoping some of this info helps and that your daughter gets help soon