The way I'm reading the bolded section above, you're talking about getting flowers sent to your MIL. If, as you say, this is what you normally do, I say continue to do so. She isn't the one who walked out on you. No need to cut her off or 'punish' her.
Oh I misunderstood, thought you meant W. That's a tough one. I would probably not send flowers so as not to irk W, but maybe send a card instead.
