Yes, you should talk to her about this. She is the only person who can give you the honest, real answer. And, if you cannot talk to her about this issue, then please consider it as a red flag and figure out why choose not to discuss such a simple issue with your live in girl friend. That does sound concerning.
Also, what she is doing is not weird. I wouldn't want anyone at my work to know about my private life. I would share if I am married but even then, it is not their business. It is better that they don't know.
Also, you mentioned that her clientele is mostly male.... So, she might end up making more tips... If this is the real reason, I would be a little annoyed but again, if you trust her and your relationship with her, you could tolerate this.