Question: Assalaamu alaikum
Once the marriage has been done and it is valid, the mother in law becomes a Mahram to her son in law. This is established whether the husband consummated the marriage or not. Hence, in the above case, it was permissible for the mother in law to hug the son in law. She did not have to wait until the marriage was consummated.
And Allah Knows Best.
Mufti Waseem Khan.
This answer was collected from DarulUloomTT.net, which is operated under the supervision of Mufti Waseem Khan from Darul Uloom Trinidad and Tobago.