Proč ne "pocitáme na ní"?
Why not "we count with her" ? (Sometimes we count numbers with her.)
Because it would then be ambiguous whether you're talking about actual counting (1, 2, 3, ...) or the idiomatic meaning, which is that we are trusting/depending on her.
Proč ne "pocitáme na ní"? Just asking a question that was already asked, but was left unanswered
because you are not counting on top of her.