Thankfully most thrift stores have "hot boxes" that get up to around 200F, which kills most insects in all life stages including bedbug, flea, roach, etc. There are collapsible models available (they pop up like tents made of mylar-like fabric) and basically operate as low heat ovens.
When workers are sorting donations they're supposed to put items in the hot boxes in batches before washing them, and putting em on the sales floor. Bottom line, Amber and Becky's junk is donatable and it would be healthier for them (and their pets) to purge the ridiculous hoard. Both of them have purchased so many fucking clothes they've never worn or have only worn once.