Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear sister, thank you for your question and for being knowledgeable about Islam’s rulings.
As for your question, if she had full intercourse with her husband, she has to wait for the `iddah period; three consequence menses. However, if they didn’t have intercourse, just foreplay, there is need for `iddah.
Responding to you question, Dr. Mohammad Qatanani, Professor in the Islamic American University and Imam of the Islamic Centre of Passaic County in New Jersey, states:
As far as I understood from your question, there is someone who had a sexual relationship “intercourse” or physical relation; touching or kissing “full khalwah” after signing the marriage contract and before the wedding. In this case, she has to stay in `iddah for three periods in case of divorce.
If the husband dies while she is pregnant, she has to observe `iddah until she delivers the baby. If the husband dies but she is not pregnant, she has to observe `iddah for four months and ten days.
In case of having the contract without any physical relation or khalwah “being in private closed place”, there is no `iddah required.
Allah Almighty knows best.