Hello Lorelai, sorry for delay, I do see your thread now for the first time.
Yes, your grandmother is right (aren�t that grandmothers always??? grin ), a shorter form could be:
Ich war Dein (or "dein" with small first letter) = I was yours.
Ich bin Dein (dein) gewesen = I have been yours.
Regards,


wotan, gd.c-b#105

"Never look for sqare eggs" as a late owner of an original FHH-dagger used to say.