That is a really complex tale Barmaid, but are you absolutely sure you have the correct lady? Certainly it would have to be a very dangerous passtime to comit bigamy on such a prolific scale. In particular, if she has used her married name to register to marry, proof of her legal right to marry would have been requested from the Superintendant registrar.
Divorce is unlikely as it was costly, what I do wonder is if they were infact catholic or some other non-conformist religion and were possibly re-marrying into the Angliocan Church, or vice-versa, which is a religious ceremony and would appear in the church or chapel registers but not in the civil registration registers.
Potentially, through ignorance and oversight, she married hubby number 3 bigamously and the second time she married him was the legal one.
I would thuink that looking at her marital status on each certifivcate at the time of the ceremony would clarify, you do get the names entered to include the maiden name and the former married name, for instance, my Mother-in Law was married under the name Joan Webb formerly Vincent, Webb being the name of of her ex husband and Vincent her maiden name.
I am not saying that you have not uncovered a bigamous marriage (or two) but the penalty if charged and convicted was probably jail.
You do need to look at the certificates to discover what has gone on and also verify that you do definately have the correct lady and that her husbands were dead or out of the picture when she remarried. The marriages of her children would show whether their father was alive or dead, good luck with that one, let us all know what you uncover.