I’ll start by saying I admit my mother in law and I are two totally different people, and I tend to fake who I am around her for fear if I’m myself she’ll realize just how 100% her opposite I actually am, from everything concerning politics, to pets, to people relations, to parenting, to things as simple as selfishness or respect of others. I admit also my opinion of her is bias because I am aggravated easily by the way she acts and treats us, so I don’t know how much of this question is me over reacting, and how much is legitimate. Here’s my problem:
She actually isn’t the one giving you the flies it is the fruit. Now, I know that is semantics, but I think it would be helpful to see that there is probably no bad intent right? So I think you could do a few things, get fly strips and just tolerate it. I think you can say anything you want. If you are going to say something try the oreo approach. Say something very complimentary to her. Compliment her on how she makes the effort to eat healthy or whatever. Then bring up the thing about the flies, How they get on things, cause distractions etc…then would she mind keeping the food outside, in a sealed bowl in the house any number of solutions, then end with another compliment. The key would be to provide reasonable solutions. If she is not willing to be reasonable about this then flies are the least of your concerns. You also may have your husband do the conversation so you don’t get seen as the evil daughter in law.