I always say the same thing when the name
Sally is mentioned: it's my niece's name, and I think it's "serious" enough. It suits her. Coincidentally,
Jesse is my brother's name, and it's not short for anything, either. I know you were asking about the female version, but I just thought I'd mention it.
I think
Sam is fine on its own, too. It's not a silly name, so why not?