A post-apocalyptic novel set after a serious meltdown at Three Mile Island. One of the characters has a mutation that prevents her from getting nutrition, except from blood. I think that one passage sees her drink blood from livestock. It had a title like Into the drift. I read it in the '90s. Paperback.
Is this In the Drift (1984) by Michael Swanwick...?
From Open Road Media:
It’s been one hundred years since Three Mile Island went into full meltdown, filling the atmosphere with a radioactive poison that would contaminate the skies for hundreds of generations. Since then, the area around the island—now known as the Drift—has been a wasteland of disease and deformity, madness and monsters. It’s been one hundred years since humanity knew what order and hope were.
The Drift has a law unto itself—one of vampires and mutants and outcasts left to struggle for daily survival. Within its bounds, the simplest act—even asking the wrong questions—can mean death. Or worse.
Praised by George R. R. Martin as “a potent new myth from the reality of radioactive waste,” In the Drift is an inventive and unsettling look at the lives of those who are left to deal with the fallout of a nuclear disaster—a towering work of postapocalyptic fiction that provokes conversation and consideration even as it produces nightmares.
This Goodreads user review mentions a mutant vampire character named Victoria:
George Martin praised it as “a potent new myth (…), an episodic tale of life, war and survival in post-meltdown Pennsylvania”. Swanwick’s writing has an incredible, beautiful density and speed, the dialogues carry wit and spirit, the characters are fascinating (Victoria, the enigmatic mutated vampire revolutionary!) and not easily categorizable (bum Keith makes all moral compasses spin around in tilt)- all the while the plot just jolts forward, sometimes with unexpected shifts of narrator or time jumps of decades.