My ex girlfriends grandma died, should I contact my ex?

You need to send a bereavement card to the family, acknowledging the death of their loved one. If she wants to contact you after that, she will. Sending her a text requires an answer from her (which is really what you want), and she may not want to answer you at this time. Don't put her on the spot like that. This is a critical time for her and her family; so put your personal feelings aside and send an appropriate bereavement card.