I have used 3 different tactics against Lady J: tarpit, paralyze and poison bomb. Flesh constructs, punk zombies, heck even a pile of dogs can tie her up for her activation. Her defense isn't stellar so you can usually keep her in place with them and use the zombie chihuahua+sebastion to get steady poison damage on her. If you are not trying to outright killer her, crooked men and nurses have readily accessible paralyze triggers to lock her down. The crooked man attack has the perk of targeting her lower defense, so it's a good use of a high crow. If you need to speed things up, there is always the rancid transplant/expunge sequence to take out a huge chunk of life without have to worry about margin of success. If you have a 12+ in hand there is no way she can avoid the attacks, even less if there are dogs near her. Plus you can do that from a distance, so as to keep McM out of her kill radius.
A fun trick if she, or anyone is low on life. The Plastic Surgery upgrade give all models in an aura 3 the undead trait. Roll up next to the model you want to damage and target a nearby friendly flesh construct or guild autopsy with rancid transplant. Give you guy a bunch of poison and do 1 damage to all the proximal undead, which now includes Lady J, or whoever is within 3" of both McM and the target model.