It's not quite the same but I completely empathize with what you're going through as a caregiver. My Mum died from cancer and she started to have daily seizures in the last few months of her life, once the tumours had spread to her brain. I was Mum's caregiver and she died at home, under my care, when I was 22 weeks pregnant with my son. My husband and I moved in with my Mum around the time we got married, so we could care for her. It's one thing losing someone you love so dearly, but losing them slowly over a prolonged period of time breaks your heart in to a million pieces.
My husband worked full-time in a phsyically demanding job and when he got home each day he took over my Mum's care for a couple of hours, so I could catch a break. I'd spend most of it crying in the bathtub though.
The rest of the time was entirely dedicated to caring for Mum, no matter the hour of the day. I wouldn't get more than a straight 30 minutes of sleep at a time, even during the night.
I'd have family members offering to help, but it's not that simple when they don't know medications (including injections), how to handle her and the changed person she was, the locations of her dozens of tumours (which would give her pain), her staph infection, etc. It's just something you don't understand unless you're living with it, hence why I only trusted my husband with it. I know that it's definitely not as simple as avoiding burning out. I wish it were.
I completely understand why you feel guilty about it.
But in saying that, the best thing you can do is let a family member in who is willing to help. I had started to do it with my Mum's sister. Don't just leave for a vacation - start with a few hours. Show them the care that is needed for your Mum and let them learn what it takes. Show them the medications, the little things that your Mum likes, how to understand her changed emotions and start from there. Stay in the house so you don't stress out and if your Mum isn't handling it well, then you're there for her.
That way not only can your Mum get used to it, but you can too. I know that we feel it as much as the person we care for, if not more!
Then eventually you'll be able to have a bigger chunk of time off and not have to worry (as much!). And you're entitled to every second of it. Caregivers in the home are absolute living angels and you should never, ever feel guilty for needing a break.
My Mum has been gone for over six years now and I do not, for even one second, regret anything that I did for her. Yes, it is so, so tough at the time to be a caregiver in the home. But I know you will never regret any of it and it will make you a much stronger person because of it. I'm sure that your Mum appreciates every single second of it. She's very lucky to have a daughter like you.