I would straight up ask her why personally! Even if there is nothing that could make you jealous, there is an obvious reason that is not disclosed in her mind as to why she is.
Maybe they are talking to her in a way that she wants you to talk to her, maybe she is showing you pics of chats to show that even though you guys are in an open relationship, she wants to go forward with you and hinting that nothing is now going on between previous potentials. Maybe she is just sending you the convos because she found something amusing and wanted to discuss or get your reaction out of.
I frequently send convos I have with others to friends. Sometimes it's because I wanted them to share in a good laugh, other times it was to show proof of words said, but most of the time, it was sent with the intent to create a topic to talk about.
So initially I would engage on the pic that is sent. Say Bob is telling a story of doing something stupid.
Oh man, can't believe Bob actually went and did that! I would be embarrassed if I did that in front of my class. I noticed lately you have been sending me pictures of conversations you have been having. Was there something you wanted to show me or talk about?
Possible Option 1:
She may say "Oh no! I just thought the conversations were amusing and thought you might get a good laugh out of it too." Which there you can make your own choices of whether to take the texts as something cryptic or not (and maybe knowing she sent it to you for amusement may take the edge off the distaste for it). Or you can simply respond:
I understand where you are coming from but I respect the privacy of conversations and would rather we find other ways to share a good laugh. I do like memes!
This expresses a dislike for it without being straight up "I don't like it". That can be interpreted in many ways, especially over text. By providing a softer approach, you are stating your dislike and providing an alternative method for which she can still share a good laugh with you on.
Possible Option 2:
Conversely, she may say something like "Oh, I have been sending them to you because I wanted to show you nothing was going on with other guys and hoping maybe we could be more serious?" Like the other hypothetical option, it's up to you on how you want to perceive that.
I appreciate you bringing that up, why don't we discuss this on our next date this Friday? Talking about this over a text message is probably not the best way! Also, next time, if you ever want to talk to me about something serious feel free to! You don't need to send me text messages of others. I would rather you come and ask me directly :)
This again allows you to express your dislike of something without coming off as jealous or uncomfortable. You let her know that the next time she feels the need to discuss with something she can come to you directly. That should let her know she doesn't need to be cryptic anymore. You also help set the example for having a more serious talk face to face rather than over a text message and, hopefully, by saying to discuss it on your next date, may alleviate any fears from you about a negative response.