Firstly, welcome to the forum. And secondly I'm so sorry to hear about the recent diagnosis. That moment when the word dementia is first used can be a real emotional blow. However, you're in the right place, surrounded by people who are or have been in similar circumstances.
It is a very steep learning curve, and it will take to learn the tips and techniques for dealing with your mother on a day to day basis. Unfortunately no two sufferers are the same and what works for one may be useless for another.
You will quickly learn which battles to fight and which to let go. You're right, you can't let everything slide, and a basic level of hygiene and care needs to be maintained, no matter what the effort on your part. Just try not to take comments to heart and know that her actions aren't always her own.
There are a lot of assistive devices available that can be employed around the home, even simple things like waterproof mattress and seat covers can be a godsend.
If she can keep herself relatively clean and safe during the day, why not change clothes and tidy the house when she's gone to bed?
Oh and just a word on the medication. You say its helping her mood, but if she's still getting stroppy is it working as best it could? I found it was important to keep in touch with both the GP and the MHNT to keep reviewing medication as time went on.
I wish I could offer a perfect solution - its what I craved when my grandmother first became ill, but with time you'll find a pattern and a way of doing things that may not be easy, but works for you both.
Sorry to have rambled! The best of luck to you and your mother, and keep in touch with others here. They're a great crowd!