Is she saving?, My dd is in the same boat work wise but we don’t charge rent as she is saving like mad for wedding and house deposit, she does however take absolutely every extra shift she can get and has been working crazy hours. The bedroom as long as it’s hygienic and I still have crockery in the kitchen I leave her to it. I don’t do laundry, I only cook for her on invitation, ie Sunday lunch other than that, we share the larder but by and large she buys her own food. I send messages grumbling if the kitchen etc is a mess as it works better than confrontation. It works well.
As far as If she loses her job due to unreliability, let her, she will soon learn. It’s not your job to facilitate her success or prevent her failure.
My one absolute red line is she has to honour her financial commitments as I won’t have my credit affected by any bad debts attached to the address, but I honestly don’t need to worry about that, she paid off her car within a year having taken the finance over 3.
The main thing, you need to do OP is learn to detach, take up a new hobby anything to take your focus, I did scuba diving. don’t discuss it with your mum, grannies can never hear any wrong, work out your own requirements for dd continuing to live with you, make them clear and decide which battles you want to fight.