I nurse in church all the time, covered of course. If she says something again, tell her if it bothers her so much, SHE can go sit in the bathroom while your baby nurses.
I wouldn't bring a pastor in it if it were me. Could become a big stink.
Keep doing what you're doing WITH confidence and she'll likely back off.
Homeschooling Momma to 19 yo DD
, 16yo DS
, 13 yo DD, 5yoDD,4 yo DD, 1 yo DD
, 1 month old DD
and 6 angels I'll get to see in Heaven one day.