While Fallon's been all about Fallon, schemes, plots and Liam did know this since he met her in one of her schemes.
Liam has every right to be annoyed, but it's not like she's acting different than normal.
Except the Colin. She never should have married anyone if she wanted to cheat.
Shouldn't Anders have cut Kirby out if he adjusted the will a week before he died? Since he had thrown her out and she was on a binge? Instead he gave the drug addict all the family secrets and money?