It depends on what adc they're playing. If it's someone slippery with some sort of dash (Lucian, graves, Cait with her net, etc) I absolutely expect the to dodge their own skill shots when conditions are right. If they start getting focused by two people, sorry that's not gonna fly. I'm body blocking as much of that as I can. Expecting them to dodge single skill shots is one thing, expecting them to dodge simultaneous skillshots from various angles is another. or heal up whenever I can maintain enough mana to do so, as well as harassing, etc. I play a lot of Nami and Braum, by the way. Braum is a fantastic meat shield. Not only does he set up a wall for projectiles, he also takes reduced damage from them. Nami heals up any light poking they take, but can't outheal an all in. If it's an adc without a dash, I still expect them to play safer, and stay at a range that they can dodge those skill shots. Same conditions apply, but this time there's not a whole lot they can do Vs a flash initiate. Even adc's with dashes cant do a whole lot against flash initiates, but ones without dashes can do even less, and they're just gonna end up taking it to the face. That's when you peel, protect, heal, exhaust the enemy, etc. whatever you can do to help them survive. If you know for a fact that you trying to save them means you're going to die, you've got another split second decision to make. Will your death allow them to escape? If the answer is yes, do your job and get in the enemy's face. You dying has the least negative impact on your team at that point. When your adc survives, they can recall and heal. When they recall and heal, they can get back to lane faster. When they get back to lane faster, they get more farm. When they get more farm, they get more items. When they get more items, they deal more damage. You doing your job as support allows your carry do their job as a damage dealer.
Now in this case where your adc isn't doing much to help themselves, and is expecting you to, basically, do half of their job for them (safe positioning) you just ignore what they say. If they're going to die and put the blame solely on you, leave them to their own devices and force them to learn. More than likely, trying to do your job as a support for them is going to get you both killed. Start roaming to other lanes, throw out some wards where you can, and keep an eye on the map for who could actually use your services effectively. Go help them instead. Bot lane is lost regardless of wether you stay or not. Your best bet is to help someone else on your team get fed in their place, because bot lane is definitely not going to do it.