I don't think it makes sense for her to say fuck it I am going to invade Elbaf if she hadn't done it in years. I think her being defeated in Wano could be the trigger for that
I always thought Big Mom being part of Wano was inevitable, and I actually always hoped other supernovas take her out not leaving everything to Luffy, however the Olin shit was garbage, her code of honor is garbage (plot device)