Hi!
It may be that your daughter has simply figured out that if she squeezes the breast, the milk comes out more quickly. Like a kid with a juice box. Many mammals engage in kneading behavior and it does not mean milk production is in any way inadequate.
Of course, milk production does diminish over time. This is part of the weaning process and is natural. So when we talk about "enough" milk or losing milk production at this age, it may help to keep that perspective about it- that less milk does not mean inadequate milk.
Personally, with my youngest child, I did experience a time in her toddlerhood where it felt to me as if there was not 'enough" milk. It is hard to explain why I came to this thinking, it was a combo of things. But personally I decided to try taking herbal galactagogues. I took fenugreek and Goats rue (I alternated depending on what was on sale) for a few months, and it did seem to help. I never tried a blend simply because I was going for the cheapest options. I took these in pill form rather than a tea, I wanted the most bang for my buck dosage wise.
Of course the most effective way to increase production is to increase milk removal- but your child is already nursing with pretty high frequency. Pumping over and above that may help, it just may be more trouble than it is worth. That is how I felt about it and why I tried galactagogues instead.
Good hydration is always good for milk production.