Erika Jayne Says Lisa Rinna Can't Be Replaced on 'RHOBH'

Erika Jayne says Lisa Rinna simply can't be replaced on "Real Housewives of Beverly Hills" ... because Lisa's the greatest 'Housewives' star of all time.

The 'RHOBH' star was out shopping Friday when cameras asked her about Lisa's recent announcement about leaving the Bravo reality TV series.

Erika says producers can try, but they won't be able to find anyone who can fill Lisa's shoes. The way Erika sees it ... Lisa is the "f***** GOAT."

When asked if Lisa Vanderpump should return to the show, Erika scoffed ... calling Lisa a "coward" who ran away from the show and couldn't face the music at the reunion ... so, not a good fit in Erika's eyes.

Remember ... Kathy Hilton gave the show an ultimatum ... vowing not to return if Lisa and Erika came back ... and Erika says she respects Kathy for coming to the reunion show despite all the bad blood.

While Erika says she's going to miss Lisa on the show, they're pretty good friends off camera and she says they will hang out in real life ... which is more valuable to her than having an ally on the show.