I'm no expert, but if it's happening immediately after eating I don't understand how it could be due to the protein levels in her food as the food wouldn't be digested at that stage.
Does she bolt her food down John? If so it might be worth trying one of those food bowls that slow down their eating, or putting her food in a Kong, or breaking her food down into several smaller meals to see if that makes any difference. You could also try putting her food bowl on a stand so she's not eating it at floor level.
Another thought, does she have a big drink of water straight after a meal? Louis likes to and I take the water bowl away for a while if I think he's drinking too much in one go as I think it makes him uncomfortable for a while.
Changing her food could also be worth trying just to see if it makes any difference, but if it was me I'd try some of the other ideas first rather than change her from a food that you think suits her.
Hope you find a solution soon