If the consideration of a religious vocation is to a Novus Ordo or conciliar order, it is probably a prompting of the Enemy.

For any reputable religious order (the CMRI sisters, for example) the time between entering as a postulant (where the candidate takes no vows) through various stages of temporary vows until the candidate takes final vows can be 6 to 10 years and even longer in some cases.  As a result, it would be virtually impossible for someone who thinks she has some sort of "obsessive" or "compulsive" disorder to rashly enter into the religous life.  The order will help in the discernment process.

The bottom line is that one does not know before exploring a religious vocation if she truly has a religous vocation.  (By the way, though I wrote this assuming the question is about a girl, the same would apply for a boy.  I was just thinking more about the convent as my eldest daughter will be entering the convent as a postulant later this month.)