Was this exchange seen by any other workers? Get your friend to write everything out whilst she remembers it. If she can get the employer to write in writing why she is being let go, you have great evidence for a courtcase. Otherwise witnesses and your friends notes are really important.

Is she in a union? Is there one she can talk to? Definately seek legal/antidiscrimination advice because it doesn't sound right.

Don't let them get away with it.