Before anyone lashes onto Gilbert, he knew Pryde before being "possessed" so whatever she did seem to be doing, might as well be a plot for whatever twisted things she did in the past.
Him saying the letters Stayle wrote to his mother were just her toying with him, were grounded solid under "old" Pryde regime.
Also, timing was so awkward with Arthur kneeling before Pryde with Stayle teleporting behind her back. Hug didn't make the situation less, steamy...
Let's hope Arthur speciality works as effective for other things than plants. Who am I kidding, obviously it will... right?