It looks, now, as though the mandatory 48 letters minimum won't be reached. Still, there's no certainty about that. More letters may be sent. It's still an ongoing matter.
Besides, Noir, you surely can't be naive enough to imagine that any Conservative MP not sending one of those letters is unreservedly happy with Mrs May. Some will have lingering doubts. How do you know that pressure isn't being brought to bear, behind the scenes, to stem further revolts ?
Consider also the breakneck speed with which Mrs May is working to get Brexit 'done & dusted'. Leadership challenges take time to bring about. We've gone from 'will the 48 letters arrive ?', to an EU-ratified deal, to a public letter to all of us, pleading for popular support for the deal .. all this, happening within ONE SINGLE WEEK !!
Oh, Mrs May is worried, Noir. She knows the whole situation is a precarious one for her, here back in the UK. Everything points to her being acutely aware of that !