If a customer complains then you have an issue you have to deal with. Either way it is a lose-lose for the company because you run the risk of pissing a customer off, but the establishment does have the right to ask someone to leave, refuse to serve them, etc. That woman would certainly make me lose my appetite. IMO, whether a natural act or not, you are in an air-conditioned place where using a towel to cover your breast is not unreasonable.
Edit:
2006 Ky. Acts, Chap. 80 Permits a mother to breastfeed her baby or express breastmilk in any public or private location; requires that breastfeeding may not be considered an act of public indecency, indecent exposure, sexual conduct, lewd touching or obscenity; prohibits a municipality from enacting an ordinance that prohibits or restricts breastfeeding in a public or private place. (SB 106)