The vamp would have actually been turned by another vampire but left for dead. She was lucky enough that Luca here stumbled upon her. He took her in as his own. Her age is up to you but I was thinking she's still very young.
The were is a family member of his ex ~peculiargirl who absolutely hates Luca. Blames him for issues within their family. The family pretty much disowned her when she got involved with Luca