I don't think the blond one was a fake friend. Everyone in the Momobami tree is messed up in their head, this applies to that Blondie too. She did what every member of that family tree would, that is gambling, both psychologically and financially. Imagine if Yumeko wouldn't have asked for the gem, then the Blondie wouldn't have profited much from that match, it was gambling for her too in a way.
I don't think the blond one was a fake friend. Everyone in the Momobami tree is messed up in their head, this applies to that Blondie too. She did what every member of that family tree would, that is gambling, both psychologically and financially.
Imagine if Yumeko wouldn't have asked for the gem, then the Blondie wouldn't have profited much from that match, it was gambling for her too in a way.