Be honest with her and talk to her about it. Bring it up casually and tell her you're a bit worried and would like if she would tell you what it is she's doing. If she's understanding and loves you she'll be honest with you and tell you what it is without making a scene. If she accuses her of not trusting her and says your being too "pushy" or "controlling" then that's a huge red flag. I know this all too well from personal experience so if worst comes to worst, gather your bearings and maybe start considering the idea of leaving as an option.