I'd have left and asked for an FP to return later when she felt better. As a sometimes noisy asthmatic myself it is *embarassing* to be the person everyone is staring at. It might be more comfortable for the child to not be in that situation. I know as her parent you feel like everyone should just be understanding but they won't be and it is awkward to know everyone is looking at you while you wheeze.
That said, the lady had no business raising the issue in front of your kid.
That said, the lady had no business raising the issue in front of your kid.