This reads like there was no GPS picked up from her phone since it was on flight mode, not like she had a separate GPS tracker.
Most likely - one less item to carry.
You can use your Whatsapp account on another phone.
WhatsApp officially doesn't allow users to use one account on two smartphones at the same time due to security reasons. But if you have two phones and need to use the WhatsApp on both here's a trick to do that.
indianexpress.com
It's annoying how these posts get bundled.
That was done as a separate post.
NEW POST - hint to Tattle devs.
Hypothetically one could leave one's registered phone at home.
Having added one's whatsapp account to a 2nd phone.
If you look at the job specs for housitting ads in Haute Pyrenees most require wood chopping & outdoor tasks.
So one could feasibly go off to the forest to chop firewood or a similar lengthy activity, making sure to be seen setting off, but actually travel to Luchon in 1hr.
Then it would take 4-5hrs hiking to get to ED.
One could call her from one's other phone. Different sim card & phone.
Whatsapp would be the same.
A person could be close by to ED on the mountain, end the call, surprise her & flip the phone to flight mode.
Imagine cops trying to get the alibi of someone who was "chopping wood" in the Arreau forest for several hours? Not easy.
And if that person's phone was at home, even more difficult.