Ah where to start, I suppose with the general thought that sometimes parts of a story "dont make sense" because they are going to be explored later on. So point by point:
1. She isn't indecisive. She's resigned to what she considers to be, and what events prove to be, an unalterable fate. Within those parameters she chooses to select the "best ending" for herself i.e. she made a decisive decision about what to do.
2. Her "followers" aren't afraid of anything. They are, very very clearly, lying about being afraid of her (Ronia) extremely powerful family so they can blame her for "forcing" them to bully the heroine, thus letting them get away with it. They need this excuse because the prince is clearly in love and backing the "heroine" so if they were responsible for bullying her they would be fucked. It makes perfect sense.
3. You should pay more attention when you read. She doesn't get exiled she voluntarily leaves (oh look more decisive action). She literally says this on pages 18-21. Ronia herself outlines the reasons for it on page 9 of chapter 1, and again on page 11. Page 11 is also explicitly about her families reaction. It's basically the only thing on the page, are you sure you read this? Her family and her (sorry to beat a dead horse, decisive) long term plan to "escape" are all covered again in more detail in chapter 2. I mean you can't have missed all this?
4. Who cares if they look gay?
5. The MC is absolutely not depicted as an airhead. She was the top of the top school for nobles for every year she was in attendance and was held in high regard by all the students for how she comported herself. The only time airhead gets mentioned is by one beastkin but only because he's in shock she isnt a big ole racist.
I mean, this may be trash, I'd say its average myself. But the version of it you read only exists in your own head.