AITAH for refusing to let my sister use my late husband's car as a "wedding gift" for her fiancé?

I (34F) lost my husband "Mark" two years ago in a car accident. Not the car in question, that one was totaled, but he had a second car, a 1998 classic he spent almost a decade restoring by hand. It was his pride and joy and he barely let anyone else even sit in it. After he passed, I kept it in a storage garage. I don't drive it much, but I take it out sometimes, and it's genuinely one of the few things I have left that feels like him.

My younger sister "Priya" is getting married in two months. Her fiancé "Sam" is really into classic cars and has mentioned a few times how much he loves Mark's car specifically, he saw it once at a family gathering years ago. Last week Priya asked me, very casually, if I'd "consider gifting" the car to Sam as a wedding present, framing it as "keeping it in the family" and saying it would mean so much to both of them.

I said no immediately. Priya got upset and said I was being selfish, that the car is "just sitting there collecting dust" and that Mark would have wanted it to be used and loved by someone in the family instead of rotting in storage. She brought up that our parents think it's a "sweet gesture" too, and now my mom called me saying I should really consider it since "objects don't matter, family does" and that I'm "holding onto things instead of healing."

I told my mom and Priya that the car isn't a spare object I'm hoarding, it was something Mark built with his own hands, and I'm not required to give away a piece of my husband because it would be a nice wedding gesture. Priya says I've made her wedding "about me" now and that Sam is hurt because he thought I actually liked him.

Some relatives are now saying I should just let it go since "you can't drive two cars anyway" and I'm being emotionally stingy over a possession. I feel like they're treating my grief like it has an expiration date.

AITAH for saying no?