Does swearing on the Quran not to speak with girlfriends and not to open a Facebook account become void after separating from the fiancé who was the reason for the oath?

As long as you swore not to do these things without the knowledge of your former fiancé while he was your fiancé, then there is nothing upon you if you do so after the annulment of the engagement. And one must beware of the whispers of Satan, for giving in to whispers leads to great evil.