Well, from what I've read, the ear tuft gene comes with internal deformities, so it's possible her sinus and eye orbits are connected in ways they're not meant to be, or something else like that causing bubbling mucus to come out of her eye sockets; another possibility is that she has a disease.
Foam or bubbles in the eye can be from an injury to the eye, or conjunctivitis, which may be from a respiratory disease, MG. I wuld cleanse the eye with eye wash or saline, and apply an antibiotic ointment. Watch for any signs of MG such as runny nose, cough, sneeze, or swollen eye.
Like many livestock chickens can hide discomfort right up until they are actually dying. It's useless to rely on signs of discomfort to diagnose disease; they can and do soldier on through some gruesome and undoubtedly agonizing or nauseating diseases and injuries like nothing is wrong. They can soldier on right up until the minute they drop. Only some show discomfort, not all.
Foamy eyes are a common symptom of some diseases, and individual susceptibility varies wildly no matter what disease we're talking about; you can (and often do) get full siblings of a clutch in which some die from a disease but others show no symptoms whatsoever. It's more common and normal than otherwise.
Best wishes. Hope it's nothing serious but definitely something to investigate.