Had to ghost a client who rescheduled five times — feel bad but was it right?

had a client reschedule five times in two months. eventually i just stopped responding to her messages. is that terrible? felt guilty but i had other people waiting for that slot and i couldn't keep holding it. has anyone else had to do this and how do you rationalise it? there's no good way to say "i've decided you're too unreliable" to someone's face.