Kim Richards -- Mother of the Bride Is Ready to Take That Walk

Kim Richards is watching her daughter Brooke Brinson walk down the aisle in Cabo San Lucas -- putting her recent rehab stay and Bev Hills arrest behind her ... at least for a day.

Kim and her sister Kyle Richards were seen gathering around Brooke shortly before the ceremony when Paris Hilton posted a video of the whole fam getting ready.

Brooke's dream wedding in Cabo is purely ceremonial -- she and Thayer Wiederhorn tied the knot last August in Beverly Hills, so Brooke's ailing father could attend.