I agree it was totally in character for Gail, the real Gail, not the simpering buffoon she has become in recent years. Gail was always strong, opinionated, able to stand up for herself, noticeably against Ivy in the first few years I was watching and Nick(y) is her golden child. Of course the lioness would come out when he's been hurt by his bride on their wedding dsy, especially as she had just discovered that his brain injury symptons have been returning so is extra vulnerable.
I'm sorry but Carla did deserve it. Yes, we know she is vulnerable, was vulnerable and upset when the infidelity happened and she's been desperate to cover it up since then so that people (including Nick) weren't hurt. But the fact remains that she was unfaithful, when they were properly together (not on a 'break') and she has gone to extreme lengths lying about it since - deceiving him into selling his business and moving away to protect her guilt. That really is a huge betrayal of trust and any Mother in their right mind would feel upset on their con's behalf - let alone one as protective as Gail is.
She might not mean to, she usually doesn't - but Carla is a mess and she continuously hurts not only herself but the people she loves (usually men) and the people close to them. I'm amazed Maria or especially Michelle can bare to be in the same room as her if i'm honest given what they've gone through and lost due to Carla's mess of a love life.