Hi Danyel!
The first sentence "I'm highly admired of her" is not correct. In this case, if you want to say that she appreciates you and she's your big fan, you can say "I'm highly admired BY her". This structure sounds too formal and unnatural, is not something people would say in everyday conversation.
HOWEVER, if you want to say that you think she did something admirable, you can say that you admire her attitude, or act, or personality characteristic: "I'm highly admired at her generosity". Here, "admired" works very similar to "surprised".
In the second example "I highly admire her" means you are her fan and appreciate her a lot.
A few examples of my own:
"I'm highly admired at my sister's attitude, she was so kind." The speaker finds her sister's attitude very positive.
"I highly admire JK Rowling, she had a hard life and now is very successful." The speaker is a fan of Harry Potter's author.
"I'm highly admired by my little niece, she thinks I'm the best." The speaker's niece has a lot of admiration for her aunt.
I hope my explanation is clear, if not, just tell me.
Take care and keep on learning!
Paola