I have not seen her since 1997保持原句意思

你是要求用不同的句型来表达吧?其实是有很多不同说法的,要看上下文和语体需要了,比如：
I last saw her in 1977.
Tha last time I saw her was ...years ago.
The year I saw her last was 1977.
It was in 1977 that I saw her last time.