Shes not dating Minamo.. So its not actually cheating if she did it.
But its very clear that Yurika likes Minamo, so doing it with Himawari here would be weird. And it will ruin her as a character for me. If that is the case, Minamo is better off with someone else if you ask me.
That was absurdly out of place story wise that it just made me laugh instantaneously. Deserves a clap honestly, since it takes some skill to ruin a cast of characters this good. I'll give it up.