How much are school providing in terms of extra revision sessions?
DD (Y11) has before school sessions every weekday and afterschool sessions 2 days a week, plus all day Saturday (Maths, English and Sciences) provided by school. Half terms and Easter also have intensive revision days in school.
We're tutoring in Maths for an hour a week 1:1 one evening a week and have seen a 2 grade increase on mock papers in a month.
But, DD has ADHD and severe dyslexia and an hour with a tutor is probably the equivalent of 10 hours attempting to revise by herself - revising with me is likely to end up with parent-child version of divorce!
Depending on Feb mocks, I may add some more tutoring in the mix. If DD's mocks had been in line with your DD's then I would be doing exactly what you are doing.
So, no I don't think you are doing too much - but I would want to see how effective it was and think about if it's targeted correctly. Getting English and Maths over the line is the priority - have you discussed dropping to Foundation level for the maths? It's one where it really is much easier to get the 4 or 5 compared with the higher paper.
I would also seriously consider BTEC L3 instead of A levels if you are having to tutor now in the subjects she wants to study. It's a different pathway and especially if SEN is involved, it can be a much better fit and doesn't mean university is off the table or anything like that.