Sorry she's talking bollox
And I would be very surprised at any company talking to her.
OH's sister died a wee while ago with no will, despite living with her partner for over 10 years her Mum was still her legal next of kin.
As we all had/have a good relationship with her partner the family were happy for him to apply for 'grant of representation' which would give him the legal right to sort everything out.
He however asked that we do this. Death was very sudden and unexpected, he was all over the place.
Even with this doc & the Death Cert we still had to jump through hoops to get everything sorted. Companies just wouldn't talk to us until they saw these docs and that OH could prove that he was the person named on the doc.
So you're left with one of two possibilities; She's lying or she has lied to this companies. Cut and paste from the .Gov website 'A surviving partner who wasn't married or in a civil partnership with the deceased has no automatic right to inherit.'
We also had to deal with Death in service benefits etc. She'd named her Mum as the beneficiary, She MIL wanted the partner to have the money and asked if they could just make the cheque out to him if she submitted a letter. No way, it had to go to her.
But honestly you need to get legal advice
I'm making these companies sound shitty here but all of them were lovely and helpful, but as they said people make sudden and odd decisions after a death, that they would never do 6-12 months later. So legally they have to follow what the deceased has said/signed off.
You as an executor have legal obligations, if nothing else protect yourself.