In Deanna, the only outward appearance is in her eyes, black as night, with no visible difference between her pupils and her irises. More often than not, it's a useful thing to appear human, especially here, where humans are not used to interacting with other species. So it's not something she generally announces, but if asked, she's happy to share.

"Betazoid. The two species are similar enough in appearance that hybrids like myself are not that noticeable." To anyone but Betazoids that is. Her weakened telepathic abilities were obvious to everyone on her homeworld.