If she had a RECENT pregnancy test, done CORRECTLY. and it said she's not pregnant, then she is not pregnant (at least, not 4 months pregnant).
She should see a doctor.
Try to find a clinic to take her to. There are always clinics in every town willing to check and see if someone is pregnant. All she will do is have to urinate into a cup and they will be able to tell you FOR SURE if its positive or negative.