Health problem preventing a spay?

ok, so I am a member of this animal group online in my area and this lady said that she doesn't want to get her kitty spayed (who has just had a litter of kittens) because her cat's mother died as well as her cat's two litter mates died from getting spayed. Apparently it is where the cat's liver can't break down the anesthesia and a genetic allergic reaction.

Should she still get her cat spayed and what should I say to her if anything?

She should have her cat tested to see if she could handle the surgery, I do believe it is liver values they test anyway.

See if she can find out what anesthetic was used. There are other anesthesia agents that are metabolized differently. She should talk to her vet, sharing the history of her cat's littermates, and see if there is a recommendation for a different type of anesthesia.