hi doinket ... don't have insight into the question you posted but do know that i was never able to take birth control, i tried everything but ended up having reactions to it all ... i would start & stop as i could feel it made me sick. only after being dx SLE did i make any connections ... it wasn't my trigger but made symptoms worse.
Dr Daniel Wallace The Lupus book talks about family connections & lupus and it is not a sure thing that either you or your sister will develop lupus, they say that siblings of lupies can have positive blood tests but NEVER develop symptoms. i would arm myself with knowledge ... enough to put your mind at ease and not soo much that you fret yourself sick ... it is mostly symptoms that they dx ... bloodwork is only 1 of 11 criteria (i think) ... read the sticky posts at the top of this message board ...
20 years ago getting lupus was probably not good as the disease was not 'recognized' and when organs got involved could be fatal ... now in medical advancement ... the prognosis is far better ... has your sister discussed your family history with her doc & shouldn't he be ordering a screening panel?
you are obvioulsy being strong for both of you & i might not know you but i love you for that ... being alone is the scariest thing for me but you have each other and you are here looking for insight ...

i would discuss birth control issues with your doctor and bring up these facts & figures that you mentioned!
some medications can be triggers ... The Lupus Book also talks about these ... see if you can get your hands on a copy (library/bookstore)
Especially if your sister is having symptoms she may really need you ... i did not immediately start asking questions & doing reasearch ... the dx set me back & i lived in denial & went along with what the docs were saying ... now i am in control & i play the biggest part in my dx & treatment. i do not take there 'word for it' anymore.
All my strength to you ... you are a wonderful person!
Angelique