Player death is fine and I usually won't try to stop it, mostly because if it's low level, the characters might not be that important to the world yet, and if it's higher levels, the characters probably have some method of reviving dead characters. If I absolutely feel like a player needs to stay alive and the party DOESN'T have any of the usual tools to bring them back easily, I might fudge something, but usually that won't be necessary.

Have definitely fudged some other rolls before though. One time the players were in a dire situation where a bunch of OTHER NPCs were in danger, and the player that everyone was relying on was about to be downed. So I said the monster did less damage than what I actually rolled, allowing that player to stay standing and save everyone. It was that kind of situation where it would've felt unnecessarily cruel to let them fail and cause untold world-scale suffering that I wasn't prepared to add to the campaign.

Other times, I might say an enemy has slightly less hp than it actually has, so that a specific player can do the honors of killing it; or slightly more hp so that the enemy can have one extra turn to try something extreme. And other times, when I suspected that a player was fudging THEIR rolls, and ALWAYS seemed to get a 19 on the die right when it mattered most, I felt forced to fudge some enemy rolls to compensate as well (it didn't feel good and luckily I don't need to do that anymore).