I really like both, and
Vera is my favourite NN for
Veronica.
I don't connect
Selma to the Simpsons at all, being Swedish my first association is to Swedish author
Selma Lagerlöf.
I would probably choose a long (three or for syllables) name as MN for
Veronica, I can't think right now of any short ones I think sound good in combination.
Selma is more open.
Example to what I mean is,
Selma Veronica is ok, but I don't think
Veronica Selma sounds good.