the purpose of romancing her for 2 weeks is because without that she will be comparing "the old MIR" with OM. he wants her to know that he is now a great guy to be with - and she will know what she is losing if she chooses OM.
I understand the rationale behind the whole "Plan A" thing. And I happen to BELIEVE in it (for a limited period of time). I just think there are other ways to show this, besides an "I knew all about your affair, but I pursued and romanced you anyway" strategy.