Both should be seperated at feeding time. Mandy and Luka are food aggressive. However, both do not care if Nova is around them at feeding time because Nova (being the smart girl that she is) would never touch their food while they're eating. However, all of my dogs are seperated at feeding time. If Molli still bites through the bars, keep Sammy away until she is done.

Food aggression, unfortunately, is very common. But also, it's very understandable.