@Jrjw - I work with a lady just like yourself, and have a similar nature myself (even though being male). The thing you have to realise is that you DO have rights (this is not wrong or prideful/unchristian/selfish), and it's not unkind to draw boundaries for people (show where the line is without resorting to anger/malice etc). Don't make the mistake that "our type" always do and get confused between niceness and others constantly getting something from you (in this case, the woman is thriving on power). There are limits, and believe it or not, Jesus himself said so:
"Be innocent as doves, but cautious as snakes".
Of course, Jesus wanted people to be loving, but at the same time he knew the state of humanity - that given the chance some people (too many) will exploit what they see as "weakness". Hence the advice to be cautious, or in other words, have your wits about you - become more aware of the situation in an unbiased way (not automatically assuming that others will give the exact same decent courtesy to yourself).
This change in perception will take time, and at first it will feel wrong, but ultimately if you care about other people's feelings (i.e. our nature, the sensing types), then you HAVE to look after yourself first otherwise you'll be so sick and fed up you no longer have the emotional energy for others. This involves not feeling like some second class citizen who has to oblige all the time to other people.
Understand that you have the power to change this situation; not exactly how others behave, but how you let it affect you. In this case, I'd go for disfellowshipping the nosey sister from your life. Believe it or not, she may reflect upon how she's been behaving....and if not, she wasn't a true friend anyway. You don't need people like that in your life.