marriage and divorce legal and Islamic

I know of a sister that was legally married, her zawj divorced her Islamically, and then proceeded to file legal papers. While she was waiting for the legal process the sister remarried islamicly. She was done with her 3 months of kullah (maybe misspelled).
I would like to know is this valid? I know of a few sisters that have done this very thing. I was told this was ok by an Imam but I have never seen the proof of this.
Does anyone know and can you show me some type of verification?

Thank you so very much.

your sister in Islam
Fatima