How to tell your lover that she is a bad cook?

The best way to tell her is to be honest about it. do it with respect. If there is something that she does cook well, then make sure you bring that out. Don't bring out all the neg things. Or you can offer to cook more often.

Why not be tactful about it. When she cooks, make it a couple adventure. Cook with her. Then you cook while she makes the salad. As you cook, have her come over where she can see and tell her, I really like it made this way. She will want to please you so will pay attention. However, this is assuming you can cook! If not, I suggest you both attend some cooking classes or get a relative whose cooking you like, to teach both of you how to cook.