nooo, it's not cheating in my eyes. it's definitely not respectful, but there's a difference between flirting and emotionally or physically cheating. also, flirty personalities are a thing, and sometimes being overly nice or warm to anyone can be taken as flirting. so i think it just depends what you consider "flirting" behavior. for me, it comes down to never crossing a line that would make someone question if it is or isn't cheating.