(1) What, if any, is the consequence or significance of being deemed "spiritually weak"?
Officially, they should be encouraged to become better Witnesses. In practice, they often are avoided, left off invitation lists (a significant burden when your social circle consists almost entirely of other JWs), and gossiped about (the phrase "Holier than thou" comes to mind). "Spiritually Weak" is not the lowest spot in the Kingdom Hall pecking order, but it's very close.
Always remember that your friend is taking a risk just by being your friend, especially with you being a non-believer and of the opposite sex!
(2) What's the deal with a JW member who is unmarried and "disassociates" herself?
They would say "Sister X is no longer one of Jehovah's Witnesses." This makes the person a Bad Association, a person with whom a Witness should have as little contact as possible (generally limited to "essential family matters" for relatives, necessary interaction in the work place, and attempts to convince them to return to the flock). Disassociation means they have given a letter of resignation to the elders (which they may have requested, with being disfellowshipped the likely alternative.) Disfellowshipping would be considered a worse status than disassociation, though the treatment the person receives really isn't much different. Both tend to be worse than a successful fade, just quietly going away while attracting as little attention as possible ("fade" is a term you will see here among the ex-JWs, sometimes it works, other times you called in to see the elders and end up getting disfellowshipped, or involuntarily disassociating.)
However, being disassociated or disfellowshipped means they can feel free to ignore the Watchtower rules about who they can date and marry. Sometimes it's a case of "It's better to beg for forgiveness than it is to ask for permission."
Recommended reading: Dating/Witnessing to a Lapsed Jehovah's Witness, at the freeminds.org web site.
