Note: this refers to book canon only.
The Tyrells worked with Littlefinger to
at the purple wedding. As this is taking place, Sansa is spirited away by Littlefinger to the Vale, the endgame of this being that Sansa marries Harry the Heir and unites the Vale with the North.
Not long before Sansa's marriage to Tyrion, there was a Tyrell plot to have Sansa taken to Highgarden to marry the Tyrell heir Willas, thus uniting the Stark house with the Tyrells.
Considering that the Tyrells were the only ones who knew what was going on at the purple wedding, and that Sansa mysteriously disappeared at the exact same time, were they aware that it was Littlefinger that took her, or is there any evidence that they might have an indication?
And considering that they had very recently expressed an interest in Sansa's marriage prospects, if they know Sansa's whereabouts, are they also aware of the Vale marriage plot?