Steph's game fits perfectly for grass, especially in the past 2 years with her being a bit more agressive on the forehand side. She is a great athlete, really low to the ground, loves to use pace to generate her own, great mover and adjusts well to low and weird bounces.
It'll be interesting against Pironkova, because that's pretty much how Tsveti is playing on grass (plus a bit more junk variety). They have played once on grass (huge battle), and 3 out of their 4 meetings were over 2h30 in three sets.
Nonetheless, very positive week for Steph with possibly her best four wins of the year (except Vesnina at AO