So this is going to be very vague for which I apologise. At least 10 years ago I read a sci-fi/fantasy hybrid novel in a library about a woman (she possibly lived in a junkyard or tinkered with broken technology trying to fix it, but I'm not sure).
She met an elven prince, possibly rescued him, ended up having what she thought was a one-night-stand with him, but woke up to find the encounter had transformed her into an elf, and that she was considered to be married to him now. She was understandably upset that she had not been informed that this would happen, but she eventually helped the prince save his people from some threat.
I can't remember much else about it.