Ok, Starlight was introduced in the last season. She was fairly powerful in spells that she knew. She brainwashed an entire village and deprived then of their talents, then went through space and time and changed the past. Yet, twilight automatically takes her under her wing. Her first friend she makes is trixie, another villian. This doesn't look too good to me. The most recent episode of her made her look really bad too. She cast a spell that brainwashed them to avoid doing the lesons. Not even thinking of her friends or how she done this once to an entire village.

Starlight Glimmer casts her hypnosis spell S6E21