I'd put this in the same category as "ain't".
While regularly used in conversation, I'd never use it in any written paper.
Ask her if that's how she would write it should she be writing a formal document.
Spoken language is generally more flexible, and I'm wondering if she doesn't mean "I've done my homework" and due to accent it sounds like "I'm", because "I've done my homework" would be proper English.
Edit to add more information
"I did my homework" is correct using simple past form of "do".
"I have done my homework" is correct using present perfect tense form of "do".
"I am done with my home work" (or "I'm", being a contraction of I am) is using "done" as an adjective, the verb is am (first-person singular present indicative of be).
"I'm done my homework" is just wrong. Done is being used as an adjective (I am done), and "my homework" is an incomplete clause.
Either you must remove the verb am and replace "done" with "did", or add the word "with" to link "my homework" to the statement.
The only way this could possibly be correct, is if people are pronouncing the "ve" of "I've done my homework" as an "m" for some odd reason. "I've done my homework" is proper (I have done my homework).
On an unrelated note, I agree Jay's answer philosophically.