Why are you asking your wife what HER plan is.. she has no plan, she's an ADDICT.
You set the pace of the marriage FOR her... you need to push her in two directions here... one of which she has to take, neither of which she will like
a. End her affair and attend family therapy to repair her marriage b. Leave her home, her husband, and her children for a reckless unproven unreliable man
She doens't like EITHER of those, she wants
c. Continue a taboo secret love affair with a married man
YOU put a stop to c, make sure she knows c is NOT available to her anymore, and then she has to go with a or b.
She doens't like a or b...she wants c.. keep pushing hard on that so she cna't have c.
If you keep pushing her to choose a or b, she will have to pick one... in the long term she will relialize A is her best choice, but right NOW she thinks B is her best choice...
If you keep pushing her and hit her with reality A will start to look a better option.
Dont' hand the planning over to an addict.. YOU plan, YOU talk to the lawyer and put it all in motion. She will squirm and yell and throw tantrums like a five year old, but eventually a or b will have to happen...
Make sure A looks as invitnig as you can make it.. WITHOUT losing your self respect.. you are NOT a doormat.. you are agood person, but good people respect themselves too.