I think Rose's approach is perfect. I would possibly add, 'And you are of course welcome to join us if you want to,' but in a very casual tone. Don't be invested in her decision or have any expectations. Think about her as a neighbor or friend - it's nice if they come, but you won't miss them if they don't.
Being the child of an alcoholic myself, I'm going to throw in a thought I had after reading your posts. Living with an alcholic can make you addicted to drama. It is experienced as painful and bothersome on a conscious level, and it will initially feel like a relief when you don't have it in your life anymore, but there may be long-time patterns of chemical reactions in the body that can make you feel bored with a 'normal' life, so after a while you may subconsciously create disruption in order to get the adrenaline rushes that you used to get from the drama created by the alcoholic who is no longer there. Does that make sense?
Maybe your WW has a need for excitement that she's not getting satisfied in a stable, reliable and predictable marriage with a solid partner. I wonder how she would react to a little unpredictability on your end. GAL-activities and pursuing your own agenda could potentially provide that. I'm really curious what would happen if you experimented a little with this.
M 16 yrs, WH62, P54 3 adult blended kids EA 11/13, BD1 6/14 PA fall 14, BD2 2/15 Piecing 2015, BD3 12/15 Separated 4/16 WH moved OW in 5/16 Divorced 6/15/17