Milady by Laura L Sullivan

Her father comes for an infrequent visit and ends up taking her with him on his return.  His lady friend at home has a son she might be interested in.  She is and she gets instructions on how to act like a lady from the lady friend.  She doesn't realize they plan to use her...

Berkley sent me a copy of this book to read for review (thank you).  It is being published today.

She helps George get to be the King's assistant and then he dumps her.  Her own father sends her to a nunnery.  Who expected her to be nice after that?

She knows poisons: how much will kill, how much will make them sick, what antidotes work.  She uses her charms to snare a young priest.  They escape together but when she wants to separate, he won't.  She ends up sneaking off.  She's out of luck, though.  He stole gold, and they are captured.  She's branded by the executioner but she gets away.  Now she can't pretend to be a lady, she's permanently marked.  But she does what she can.  She even gets married but won't let him consummate the marriage.  Then she learns about his temper.  He's a wicked man.

She really just wanted a man she could settle down with and have a family.  It's not to be.  With her poisons she leaves dead ones behind, she's escaping old enemies until they find her again and she's close to death many times.  She doesn't have a tame life.  She doesn't have love, just the power of her poisons and her personal strength.  Will that be enough?