Oh you let your ADC die if they do stupid stuff, especially in your Elo.
Always let them die. After they die a couple times in a row from you not following up they will learn. They may complain a lot but they will, typically stop dying or try to avoid it. Stay in lane with them until 6 and then roam. Ward or go mid. You don't need to always be with the ADC if you are support.
In general, your job is to support the carry (which could be anyone on your team). If that isn't the ADC, your mid laner, jungler, top laner, are doing well, you help them out more.
Lower elo players are in the mindset that the support is just meant to help the adc only. That isn't the case at all. Your job is to help the person who gives you the best chance to win on your team.
It is much worse for you to die alongside the adc from them doing dumb stuff while you are trying to save him/her.
Never help bad players when they keep making mistakes, because they will keep making them throughout the game.