Hi !!!
Here in Italy
Tessa is a standalone name. I think that very few people would link it with
Teresa or even Contessa.
I've always liked it. I adore its sound. It is simple to spell and pronounce in any language. It doesn't need any nickname. I personally link it with yellow so it's a bright name in my mind.
Personal Name Lists
https://www.behindthename.com/pnl/125456