My mother-in-law made this comment to me

A few weeks ago, my MIL and I were talking about something. I don’t remember what the conversation was about , but at one point of the conversation, she said:
“things that I tell him (my husband) he shouldn’t always tell you. and things that I tell you you shouldn’t always tell him”. I thought it was an odd statement to make. I feel like the statement was made as an outlook outlook of: “don’t tell each other what I’m telling you each separately so I can control the narrative.” That’s basically what I got out of that comment . I’m not sure if I’m overreacting to this statement. would you find it weird if your in-law said this to you? Again I’m not sure what the conversation was about. I believe we were just having a general conversation. And one time my husband and her got into it and she made that comment to him as well. I feel like if she were to make that comment again I want to say to her don’t worry about what my husband and I share to each other because it’s our marriage. But I also don’t wanna cause any tension either by saying something like that. Thoughts?