How much did they bring? If they brought a bunch of panties, they may not need you to do much for them. I personally don't wash my bras constantly, so no bra for the wash in 5 days would be normal here as long as I wasn't sweaty (and I shower daily). Now, I'd bring more than one bra for 10 days but maybe she didn't think ahead.
If they smell, then you need to address it. Tell them that by x time tomorrow, they must bring you all their laundry or run their own by x time and they must also take showers. If you are going on an outing, make their cleanliness a condition. I would deal with it in your home, not call the girl's mom.
In the summer especially, I have had the experience from a number of teens (friends, the stepkids, their cousins) that sometimes you need to be a little blunt and point out what they don't notice. My SIL once came over and said to SS, "I'm not hugging you til you get a shower." (A few years later he planned for one pair of jeans for 3 weeks travel in Europe. I said that was gross.)