YOU SAID:
I last saw grandma when we went to her house last spring
INTO JAPANESE
私が去年の春に彼女の家に行ったとき、私は最後におばあちゃんを見ました
BACK INTO ENGLISH
Last time I went to her house last spring, I saw grandma
INTO JAPANESE
去年の春に彼女の家に行ったとき、おばあちゃんを見ました
BACK INTO ENGLISH
When I went to her house last spring, I saw grandma
INTO JAPANESE
去年の春に彼女の家に行ったとき、おばあちゃんを見ました
BACK INTO ENGLISH
When I went to her house last spring, I saw grandma
That didn't even make that much sense in English.