Dany’s plan all along was to take the throne “by whatever means necessary.” Despite an occasionally kind heart she always showed a disposition towards violence and the worst kept secret in Westeros was that she would torch the place after everyone closest to her had either been killed (Jorah, Missandei), misled her (Varys, Tyrion), or rejected her (Jon). The only “ally” she had left was Grey Worm, equally disposed towards violence and (now) vengeance.