Doesn't she look old!=She doesn't look old at all.她看上去一点也不老啊!
She does,doesn't she!她确实（不老）,可不是吗?
如果将第一句看作是原陈述,并且后面带着反义问句,那么句意就更好理解了.即：
——She doesn't look old at all,【does she 否定陈述,肯定反问】?
——She does=【语境承接——她确实看起来不老】,doesn't she!
这里正是因为这种实际表达中的省略,导致理解难度加大.