I like
Victoria too much to mess with it and use Plum as a nn.
I know a Chinese woman who went through a phase of asking everyone to call her Plum instead of her very pretty Chinese name, which has something to do with fruit or forests or something ... but it never caught on.
I would use
Vickie if anything, because of a very good friend whose parents reasoned that they would always and only call her
Vickie so they might as well make it official.