It's pretty simple-

You’re expecting her to be who you want her to be, rather than who she is.

In your mind, you care for her, but you see that the relationship could be better, possibly even with very small, insubstantial changes.

In her mind, she appears to see those discontentments that you’re expressing about her as a rejection of her, rather than as motivation to grow.

This could be because…

• She is too rejection-averse, or confrontation-averse, and feels very stressed when others are not 100% approving of her.
• Your comments trigger low-self-esteem or other self-image issues that cause her to withdraw.
• She doesn’t know how to change those things.
• She doesn’t want to change those things.
• She is “allergic” to anyone telling her that she should be different.

There are many other possibilities.

In short, she's ghosting you because she is feeling some form of emotional pain, perhaps...

• Fear - that you'll dump her if she isn't able to change
• Sadness - that you're not happy with her as she is
• Anger - that you're asking her to be someone different
• Annoyance and Resentment - perhaps that you she's accepting you, but you're not doing the same for her

Relationship worldviews

My guess is that in your mind, relationships are about compromise, balance, growth. In her mind they are about two people coming together as-is, and it either works or it doesn’t. You don’t “become someone else.”

In a sense you’re both right. But more importantly, whichever relationship worldview you each have, they need to match or you’ll encounter confusion and frustration just as you are here.

What you can do

Talk about the underlying relationship worldview before you talk about "how to change" for each other.

Explain to her that in your mind a relationship is about growing and changing together, towards creating the best possible relationship for each other.

You may discover that you're aiming for very different things, or that she has a very different idea of how relationships should work.

A few final notes

Maybe you see wonderful ways your relationship could be better, and you want to share them. Maybe she does too, but she’s not sharing them.

Always be aware that “perfect” is an idea.

Real people aren’t perfect. They have great days, and sucky ones. Wonderful traits and crappy ones as well. Embrace all of them. Chances are she has lots of things she’d change about you, but that she doesn’t seek that change because she cares for you just as you are.