Yes.  Darling I hate to tell you this but even under Humane Vitae condoms are allowed for prostitutes.  A prostitute does not incur an additional sin by using a condom when having sex with her clients.  In fact a sex slave like the woman being helped is not in mortal sin.  She has been forced there and has no recourse.  These women may not be willing to accept help at first but may accept free condoms.  That may be the first step in helping these women.