1. Different patients mean different things when referring to starting menopause. By definition menopause if the total cessation periods while perimenopause is the typical year or so preceding menopause. Symptoms are different and treatments (if needed) are different.
2. Specific symptoms? Hot spells,night sweats, sleep disruption, libido issues, atrophy or dryness issues etc. There are so many symptoms with different treatment options that a detailed discussion is just not possible in this forum. I would suggest she speak to her health care provider and determine what is perimenopause/menopause related and what might be an indicator of some other health issue.
Otherwise just drink to comfort. Drinking excess fluids to 'flush' your system out is a fallacy and you will just urinate more. Elevating your legs will help some but generally as soon as you stop it will return. Rest assured as long as your blood pressure behaves it will go away after delivery. And unfortunately yes, it can get worse.
Doxycycline is most commonly used to treat suspected cases of Chlamydia or Gonorrhea, but that is not the only use. Can also be used if suspicious of pelvic infection (uterus, tubes). Could also be used to treat any skin type of infection of the outer vulval skin, although generally not the first choice of antibiotic for that. Could sometimes be used to treat possible bacterial infections of the vagina when not responding to other antibiotics, but again would have to know what her provider was thinking. Could also sometimes be used if provider thought she might have a chronic low grade infection of the uterine lining (AKA chronic endometritis). Hope that helps some.
Kidney stone a possibility, but most likely would take an ultrasound or other type of imaging to detect. If OB related, could be an ectopic (tubal) pregnancy, but if that is the case, a pregnancy test would be positive. If so, these are emergencies and need to be evaluated and treated immediately.
If you are not on BCPs, then could be an ovarian cyst or an issue tied to ovulation. If that is the case, should hopefully fade with time. Ovarian torsion is also a possibility, but not likely to last this long. If persists or progresses, then needs to be evaluated and if fever/chills or positive pregnancy test, needs ASAP evaluation.
This is a very broad overview. Do not hesitate to seek medical advice if you have concerns.
#1. Hopefully, your mother and/or grandmother are still living and if so, have they ever been tested for the breast cancer gene (BRAC)? If not, I would highly recommend that be looked into. If they are positive, that would increase your risk and would highly recommend that you then be tested. If they have been tested and are negative, that would provide you some protection, but you still have a significant family history.
#2 when should you start having mammograms. You can start them at any time, but they might be less reliable in a younger woman given density of breasts. Also, concern with exposing your breast/chest to excessive amounts of radiation. Some experts would advocate you undergo MRI examination of your breasts since it does not involve radiation, but that is a costly test and good chance your insurance may not cover.
#3 if undergo mammograms, then difficult to know how often that should be done or when to start. I would think 30-35 would be reasonable and give you several years of screening prior to the onset of your relatives disease.
#4 might want to consider genetics consultation to assess your overall risk of breast cancer and also they can help recommend screening strategies.
#5 need to have regular breast exams by medical provider and monthly breast self exams are also very important.
Good luck and hopefully this will provide some basic guidance.