Juliet knows a lot more than she's ever let on. She speaks Latin, knows Richard Alpert is "really old," and has lived as an Other for several years. She's clearly privy to at least some of the Island's secrets despite not sharing them with the Losties. There's a reason for this: she wants off the Island because she's tired of failing at her research and misses her family. But she may still have an affinity for the Others, the people she lived among for years.
She's now in a relationship in 1977 with Sawyer and may have put her days as an Other behind her. But she may never share what she knows about the Island with the Losties out of loyalty to her people. I really curious to know what she knows, as her facial expressions were very revealing during "La Fluer. She seemed to be less surprised by seeing the statue, she knew exactly what the sonic fence was, and she even hinted at her affinity for the barracks when she mentioned which of the houses was hers.