Schiavone's playing better right than you give her credit for. You don't get to the Quarters of a slam, beat Kvitova in style and be outplaying Sharapova until shitty weather halted her without being in good form.
Experience plays a big part in it too, not just mental fragility. Many of the less experience and lesser able players choke and can't convert the big points. That's a large part of what makes the elite players the elite, that ability to win the points that really matter. How often do players break a better player than themselves and then lose their serve straight back to them. Same for converting break/set/match points. That's the sort of thing that will come with more experience at a higher level playing singles. Doubles is a totally different match and not just playing on a wider court with a partner.
Robson up to #57 Top 50 by the end of the season should be plausible now and then maybe a seeding for Wimbledon? I was partly trolling Murray fans when I said she'll win a slam before Murray but I do honestly think she'll reach a Slam Semi in the next 2 years once she starts getting easier draws. Outside of Serena and probably Azarenka, all the womens players are very beatable on any given day.
Still doesn't change the fact that Shvedova should have beaten her. This is a very disapointing loss for her. Her confidence must be completely shattered, and thats bad. Shvedova is a confidence player, and this year has been a clear example of that. She was confident at RG and Wimbledon, where she played some great tennis and pushed top players to the limit. No confidence, and losses like this happen. I've nothing against Fran at all, but Slava should be winning these matches if she's to reach her target of top 20 by next year.
And what you said on mental strength is right, but with Slava it's something else. She's choked so many times this year i've lost count. It's not like she's new to the tour either. She's been pro since 2005, and is in her "prime" at the moment. She's never had much mental strength, but her recent chokes have been laughable. Also, her recent chokes have been 1st and 2nd round. It's not like she's in a whole new experience here. She's a 2x Grand slam Quarter finalist. With some players, your theory is spot on, but with Slava it's something else. And it needs sorting if she's going to reach the level i think she is capable of.
As for Robson, she looks like she may have a good future, but i think the hype is getting a bit overboard. She's 18, so she has plenty of time to reach a slam semi. I don't think she'll do what many are predicting her to do in the next few years. Not hating on her, she seems like a lovely woman and all and i think she can have a good career, but i just think the hype needs to settle down a little bit. Top 50 by the end of the year is very plausable though and should be her goal for the rest of 2012. Seeding positions by Wimbledon is possible, but i don't think it will happen.