While I am sad we will no longer see further adventures for Glimglam (and the rest of the cast too, of course) I don't think she did badly either; she got similar exposure to that of the CMC, significant character development and screen time, and a fair amount of walk-on parts in episodes that weren't focussed on her. Her roles in the two-parters are also well above the norm; S5 and S6 both have her playing key focus roles in both premiere and finale, which until then had focussed on Twi's personal growth - Co-focus in S5, and not sharing the limelight at all in S6. So... yeah. I don't think you can say she has been slighted by the writers.