First things first.. DO NOT GET YOUR COLLEAGUE TO CANCEL THE WORK PERMIT.
Just fill up the form for the IPA on MOM website online.. Make sure you've got all the details such as her passport number and stuff. (and your colleague's consent)
Once your IPA is approved, call NTUC hotline to arrange for the insurance and security bond..
Once that's done, you can ISSUE the WP online.. then there will be a notification letter telling you what to do (on a certain date). From the day you issue the WP, the helper is urs.. and your colleague is no longer in charge of the maid. Hence, no need to cancel the maid's workpermit.
LET ME WARN YOU - if your colleague cancels the workpermit, the maid has to go back within 7 days.