If I'm right about what Azusa intended to convey, it's notable in that it's not actually telling her to back off or saying anything at all about what Azusa's intentions or thoughts are about the whole thing. Instead, it's almost like she's guiding Amatella towards properly considering her own feelings about Yuuta - if she cares about him, she should back off and let him live his life, if she has romantic feelings for him she should consider how she wants to act on them. I can't help seeing that as a kind of careful parental-style guidance of a child's thoughts down a path that will (hopefully) help them grow as a person - which is definitely something Amatella could use some help with . . .
At the very least, her words and actions are entirely aimed at Ametella. Asking her to consider who she is to Yuuta, and who she wants to be. It's an almost agonizingly thoughtful and mature way of handling that, because Ametella intended to drag her into a fight, revealing Azusa's intentions, but instead we get
nothing about how she feels. Which is, well, the central issue.
Azusa very rarely SAYS how she feels. She demonstrates it. She touches, she leans in, she grabs, she rests against, she wipes away tears, she kisses, she tickles... but all these things aren't read as genuine or clear. They could be fake, you know. Even though people can lie with words, as well.
If you want to be charitable Azusa is forcing Amatella to move, either toward Yuta or away from him. That's actually good for Yuta because having an obsessed possessive stalker fan is rarely a good thing. You just need to look at idols to see the same thing with genders reversed.
I don't really think there's a reasonable reading of her words and actions that doesn't come to the conclusion that she's challenging Ametella to decide what she wants. She makes her answer that she's not Yuuta's girlfriend, and then says that she shouldn't try to tie someone down, especially if they care about them. When you consider that she said that she's Yuuta's friend, but isn't sure if he sees it the same way, you can't really take it as anything else. She's not claiming ownership of him, and tells Ametella that she shouldn't, either. What else could that mean?