I think any dog that has always had its people all to itself will initially resent the 'intruder'. However, like you say, given the right steps and patience it sounds like Lanee might do well. Would probably suggest a male, on the younger side as a general rule of thumb.
Part of contemplating also includes reworking budgets, time tables, and all things dog. I love my boys and they do great together. I honestly think they make each other very happy, but they will always be happiest when they get my undivided attention individually. Twice the dogs is twice the work.