Question

why doesnt juliet want to mary paris

Answer 1

she doesn't love him

Answer 2

Contrary to what Lola told you, Juliet never says that she dislikes Paris or finds him arrogant. (In Act 2, Scene 4, the Nurse tells Romeo that Juliet can't stand Paris. Juliet herself never says so.) But by the time her father announces that he has arranged for her to marry Paris, Juliet is already secretly married to Romeo. If she went through a wedding ceremony with Paris, the marriage would not be valid, and if she went to bed with Paris, she would be cheating on Romeo, the husband she loves.

Answer 3

what @crazycocob said

in basic terms: she doesn't love him. she loves romeo not paris and does not want to marry paris.