considering Juju moved on and had a kid, and since it doesnt seem like theyve continued their thing into adulthood despite having plenty of opportunities, seems to me like the Queen always knew her thing with Juju was going to be short term
and just because it was an arranged marriage doesnt mean she had no choice, Momo has a stack of suitors as the third princess so Mari should have had other options, im betting that the two of them had a few dates and if they decided they didnt like each other it would be called off and a different suitor would appear