I have confessed that I have very mixed feelings about Lady Russell, and I find it interesting that this quote which you give in support of her is one I had marked as being a negative! ;-)

"and vexed her as much when she was away, as a person in Bath who drinks the water, gets all the new publications, and has a very large acquaintance, has time to be vexed."

I took this to mean that, yes, she was concerned about Anne's situation when she was in Camden-place. But once away from the house, she was so busy doing this and seeing that, that she hadn't time to worry or try to do anything to improve Anne's situation. Her concern is no longer "perpetual."