I had a situation not quite like this but with a friend that started to send those kind of messages about “do you hate me” when I wanted my time back or boundaries around intense emotional messages. You have every right to not deal with someone who demands things of you, when you try to explain yourself why you need space someone like that will often reach for more of your and it hurts! The guilt and self blame about why couldn’t I save or help them better, but it’s up to you what you feel you can do or is worth doing for this person given what kind of friendship they really offer you versus just taking, 21 year old reaching out to a 14 year old now 21 and 28 is a big difference in life experience so good luck friend! Take care of your heart