Hi slug.
I too often have to go to the toilet A LOT. especially in the beginning of the ride. But I have noticed (and you can tell your friend) that it's better to get right back on the saddle, because lounging around you tend to stiffen up.

do address this with her; she might see reason. But some of us really have to go a lot.

ps, again, if she is bragging, if it's worth it, let her brag. But you don't have enough time in the day to go home and take naps in the middle of the ride! (and I'll bet neither does she!)