Universal law of romance stories, both straight and yuri. I will also love wingman characters. Especially when they have that smug, knowing look. The wingman basically represents the audience, in helping the couple get together. It's like I get to participate in the story as a side character. What fun.
What was really masterful, was the way the author initially introduced Garth as a love rival. I was all prepared to hate him initially. That was a well executed twist!
And on a more serious note, I think the author did a good job of justifying why Yvonne is trying to setup Elsa with a guy. We still don't know the full context of what happened on the beach. But we know that whatever the Villainess System required of Yvonne, somehow resulted in Elsa being injured. In the very first chapter, the system wanted Yvonne to murder Elsa on that rooftop. There is a real and present danger that there may be other requests like that. With that sort of danger, it's no wonder that Yvonne is doing what she did.
The whole situation is so messy. I don't think Yvonne should keep trying to shoulder this burden alone anymore. I think she should tell Elsa about the Villainess System. If Elsa knows about it, they could work together to find the best solution, as each new task appears. I also think they should try and find out what exactly the system is. Is it that god of this world? A demon lord? Perhaps research could shed some light. But instead we have Yvonne trying to stoically bare this burden on her own.
That being said, please don't spoil what happens. I'd rather read the story as it progresses.