How will the property of an unmarried non -Muslim woman be divided after her death?

A family member (non-muslim, ex-pat, female) passed away. She was registered in the UAE and has a UAE working/residency permit, alongside a company registered in the FFZ. It appears there is no will. She has no UAE real estate. She has no children and was never married.

She has a living mother and sister, alongside an adopted sister with whom no one has a contact.

1) How will heirs be decided? Using home country law or sharia? Can we choose? How do mother and sister show proof of lineage?

2) Using the inheritance law of our home country, the adopted sibling is seen as a full sibling. It will be a 1/3 division between the three persons stated above. Can a court in UAE overrule this part of home country inheritance (e.g. incompatible with UAE laws) and skip the adopted sibling?

3) Can legal heirs (e.g. mother, full blood-related sister) agree to a different division if heirs are decided? E.g. the sister wants to include her children as heirs. Or does this have to be done after the money transfer?