解释一道SAT语法题( Until revealing that she had been working )at a

这其实是not...until的句型,few体现了句型中的not.
Few of her friends realized that Amanda was interested in art,until she revealed that she had been working at a design firm.这是最原始的顺序,应该能够理解吧,she指代的是Amanda.
几乎没有朋友发现Amanda对艺术感兴趣,直到她表明她已经从事过电影设计了也就是说：直到她表明她已经从事过电影设计了,她的朋友才知道她对艺术感兴趣.（而且完成进行时表明这个动作也还可能在进行中）.
而这题只是调换了顺序.
此处的until是连词,后面应该接一个句子.