My DS is in nursery 2 days a week, and I don't even have any work on, on some of my days off! I have felt guilty, on and off, for this, because (a) it's uncomfortable that we can afford it and (b) I feel a bit guilty for the time.
However:
(1) It has improved our relationship no end, for me to have some time to do things fo rmyself, housework, admin (e.g. paying bills), seeing people without him in tow, shopping without him, etc.
(2) He has gone through loooong phases of crying demonstratively at my departure, but he can't cry and mope all day long, because there are things he knows and does now that he could only know and do if he learned/did them at nursery. This includes singing, painting/craft and puzzles. Nursery has got lots of toys we don't have space for, and he sees other kids and is being nicely socialised. Social eating is a big thing there, too.
(3) This is probably a d--- sight less disruptive than have a babysitter, yet a babysitter might be seen as more acceptable to your mother, so you see, any guilt is being enhanced a little bit artificially here, isn't it?!
As long as you are happy with the nursery/childminder in the first place, leaving your child in a safe environment without you is not truly dreadful.
There are only a couple of caveats to this:
(1) no nursery I looked at would take a child for less than 2 days.
(2) 8 months old can be the height of separation anxiety, so it would be a hard time to manage it. Sorry!
As for your mother, why is she guilt-tripping you about being a terrible mother instead of saying or doing something helpful?
P.S. We moved when DS was 8/9 months, but what with crawling and getting into all the boxes, and my being afraifd I would drop something on him, it would have been good to have had him out of the way!