I don't know what to make of the statement in your second paragraph. Are you saying that UConn's experience with Molly and Kyla has been a bad one and has soured Geno on taking other players in that mold? If so, I think you are completely wrong. I think Geno and CD appreciate how much those two have contributed to the team (without demanding mucho minutes or threatening to transfer if they don't get those minutes), and they would be delighted to have two more players of that talent level with the same attitude, to fulfill a similar role.
I don't know whether Caroline Ducharme would be right for that role. You may be right that she thinks she is talented enough to be a starter in college, and she may be right about that. It does seem unlikely that she would be a starter and play major minutes at UConn in the next few years. But she is from nearby (the Boston area), so her family could attend many games at UConn, and she may like the UConn style of play enough that she is willing to take that risk. As a non-superstar, it seems unlikely that she will play in the WNBA no matter where she goes to college, so playing minutes may not be critical to her from that point of view. (That is in contrast to someone like Mikayla Coombs, who may well have WNBA aspirations, realistic or not.)
The most important question is whether both Caroline and UConn Nation could accept her as "CD 4".
If Caroline comes to UConn and (if necessary) accepts the Molly/Kyla role, it would not preclude Geno from signing a 5th player from the 2021 class who might actually be a contender to start during her career.