Cassie, wont Elope that Far all she will do is go back to the Abandoned town Safehouse.
You can continue the game as Normal.
Get Arlenes Assistance the Shark at the Police station.
If you cause a Riot and then prove that the Don is doing illegal Operations Aka Slavery she will ensure the Don wont come for you ever again.
By beating him half dead from Ecstacy...
To Cause a Riot, in front of the Dons home go down and talk to ALL the beggars, pay one of them 2k Bits, sleep, afterwards talk to the beggars on where he is they should tell you that he is at the "Gentleman's", the Striphouse beside 'The torture Rack' scare him he will return 500 Bits use that to Pay the Beggars for a Second time, return to the Slums under the Dons Home and pay 500 bits to cause a Riot, then talk to Arlene, if Arlene, gives you Praise she should have your back when you Rescue Cassie.
Then you can Continue the game as you wish.