Translation:I have found that she is very tired.
"Boring" would probably be "chata" used with the verb "ser". "Bored" (which is probably what you meant) means something slightly different as I think "cansada" signifies that she is worn out and weary even though she may or may not be bored with what she is doing. I get tired from studying Portuguese, but I'm not bored of it. I think "entediada" might be the word for "bored" in Portuguese.
A native Portuguese speaker will have to confirm though. If so, the suggestion may be incorrect.
Edit: According to wiktionary, the 3rd definition is "aborrecido" which seems to translate to "boring". Maybe if the verb is "ser", but I'm unsure.