QUOTE(celloml @ Jun 3 2011, 04:31 PM)

so she says that silent fingering practice is a fine way to improve left-hand dexterity.
Yes this is an excellent thing to do and really improves speed and accuracy. It makes your left hand really really secure. When some people play fast quiet passages it can sound scratchy and unpleasant because their left hand is insecure and they feel stressed (consciously or unconsciously) and that stress feeds through the bow and then out comes an undesired sound.
I would say use the late night practice time to work on the left hand alone. You should be able to hear the notes you are playing as you press your fingers down on the string so you will know if you are in tune or not.
Other things to do are to spend time thinking about interpretation and adding dynamics to your score.
Another good thing to do is video yourself playing. You could video yourself at a suitable time of day and then spend time late in the evening watching the video (the sound doesn' t have to be heard by the neighbours) and analysing it, looking for some good points and points to improve. Then look for some exercises to tackle the improvement points and list them so that when you do have a practice time at a sensible time of day when you won't annoy the neighbours, you can get straight on with it. Investing time in creating a practice plan for a week is definitely worth it. I did this a lot when preparing for piano grade 8 and yes I am going to get back to some serious study of the violin and practice planning will be a big part of that. - but probably in mid July when things calm down. It is manic here at the moment.
Oh yes and further rambling - sometimes I bow the orchestral parts at night. I use the bow but just move it up and down in the air and try things out, then write the bowings in.