My novel is written in 3rd person from the perspective of multiple characters

[Guest]

The two characters lives intersect.

The one main character is referring to her mom (Mary) in past tense as she has died before the story starts.  I have written this referencing the mom as both "her mom" and "Mary" but I feel it's confusing and that I should stick to one or the other. 

Which one would be the best?

[Delphina]

I’m confused as to how it is omniscient but two different points of view.

[Lynn]

Be very clear which POV you are in for a particular scene. Use dialogue to keep it clear. Her POV should always refer to Mum, but others can say Mary. In other POVs refer to Mary in the narrative.

[Charley]

Yeah that's not third omniscient.