it is not even Halala.. there is no such thing
the real story is like this, that in Islam once divorce is finalized, there is no way that the couple can re-unite… only one way is there, that is, if the women get married to someone.. and that is having no intention of getting a divorce or something like that.. and during the normal course of life she gets divorce or ( get widow, i am not sure about the widow part) then only she can re-marry to her ex-husband… and this course of life can be of many years… so there is actually not concept of halala but someone just came out and made it