If it is not healthy for her, she canít have it . . . period.
Source: My Daughter Has Celiac Disease
What is the goal/intention of utilizing the word period at the end of this sentence?
It emphasises the statement and its finality.
'If it is not healthy for her, she simply can't have it...there's no more to be said...simple as that...end of story.'
In BE way '...she can't have it...full stop'.