Its easy to have 'drive' when you aren't working full time, have two children and are maid to a man.
Its easy to look amazing and 'not let yourself go' when you don't live with your partner full time, have two children and are maid to a man.
He's seeing the OW done up to the nines to impress him. The other days of the week, she's probably secretly slobbing out in tracking bottoms or stressing over what next she needs to wear to impress him because she is jealous and concerned about the OP and how he is still with her despite professing his love...
And thats the rub. The second she's living with him 24/7 and he's putting in his order for dinner and complaining about whats she's serving him, I wonder how long she'll continue to scrub up for him 24/7. And at what point he regards her as having let herself go or complains that she's a useless cook and how his ex used to feed him so much better.
The reality of him moving abroad and her not getting a visa will be an eye opener for her. How long before she starts to worry about the mistress or when his next visit might be. And how long before he starts saying 'oh i can't come back to the uk, cos i'll be done for maintance if I do'.
Revenge is a dish best served cold for all these reasons. Its enough to know that the fantasy is not reality. No need for fish.