I'm sorry I just have to suggest ruling out Lyme Disease as a possibility for you and your sister.
The current tests for Lyme Disease are not reliable and diagnosis should be by symptoms and previous exposure to ticks/history of tick-bites.
Its just that you describe such intense anxety, random pains and the fact that your symptoms increase at the same time as your sisters. Perhaps a coincidence or psychic sisterly bond.
However, many of us on the Lyme forum experience an increase in symtoms at certain time in the month, for myself corresponding with my menstrual cycle.
If you guys have any other odd symptoms like insomnia, early waking, cognitive problems (such as poor concentration, forgetfulness) tingling or numbness in extremities, muscle twitching etc. it might be something to look into.
Just a suggestion. I wish you & your sister best of health in any case. PEACE!