Crikey. So many experts giving such differing advice!
Fwiw, re. the scary anecdotes about brain damage from hypoglycaemia and life threatening dehydration, don't panic :)
Look at your baby. Keep an eye on her output- if she has wet and dirty nappies, there is getting milk. Look at her fontanelle on the top of her head, is it sunken? Do her eyes look dry? Does her skin took plump and pink? Does she produce tears?
Is any jaundice improving? How is her behaviour? Angry crying and sound sleeping are good signs that she isn't hungry and has enough energy to cry. Bad signs are listlessness and lethargy, and whimpering cries- no energy to cry, or to put them in a good sleep.
Look at the whole baby. There will be clinical signs if you look closely, well before you get to a life threatening or life changing point. If you are worried seek medical advice as dehydration and hg can be serious. Better to do something and be told she's fine.
But everything being well, if yoi are determined to bf, the beast thing to do is bf. Faffing with expressing or topping up will prolong this initial phase of getting supply established.