M.P.
Does she live in an apartment? If so the apartment management should hire a pest control company to treat all the apartments that have roaches and to continue doing so every month.
If she lives in a house, I recommend that she hire a pest control company to treat her property. They know where to find the roaches and where to spray. Roaches are nearly impossible to totally get rid of. To come close, one has to keep all food in closed containers, even garbage, and to not let so much as a crumb stay out.
The pest control company will give her more info. You can also look them up on the Internet.
My daughter lives in an apartment and even when she's roach free a new neighbor will move in and before she knows it she has a couple of roaches. She calls the office and they put her on the list for the pest control company. She usually finds them first under the kitchen sink where she keeps the garbage. It's next to impossible to keep that area spotless.