Its the in thing for runners and cyclists at the moment. Probably also a reaction to having trained in Flagstaff in the snow and then racing in a "hot" London.
Problem is she's doing active heat acclimation (exercising in the heat/increasing core temp through layering up), which increases the intensity of the bout of exercise - we all see it when our HR/RPE is higher running in summer because its hotter. It'll mean she should be absolutely shuffling on those easy runs in lots of layers - which I doubt she is!
Hoping she's being guided through it, personally I'd almost always stick with passive acclimation (hot tub/sauna) and just do 20-30 minutes a day - she could even optimise her time and do her socials whilst doing it.
It's funny seeing this take off, as I'm just about to start recruiting people for a study on it, and how wildly far off the mark/more complicated influencers and unguided athletes make it. Really makes you question their advice if they do things like charging £180/month for coaching!