I think if she were my daughter I'd do as I was doing at home.
But if your sister (her Mom) feels more comfortable going ahead and just putting her in Pull Ups most of the time, just let her. A little potty training regression may be a small price to pay if the Pull Ups will help Mom have more of a worry-free trip.
But if your sister (her Mom) feels more comfortable going ahead and just putting her in Pull Ups most of the time, just let her. A little potty training regression may be a small price to pay if the Pull Ups will help Mom have more of a worry-free trip.