EQAO is optional in Ontario. All you have to do is send a letter to your child's principal stating that you do not want her participating. Period. They will give you a hard time because they still have to report her score as a zero and, as someone else already mentioned, a low score is still better then a zero score. In a small school that really messes things up and schools hate seeing their name low on the published rankings. I've taught at the highest ranked schools in Ontario (according to EQAO) and I'm telling you the test is meaningless. Well, it's been good for my home's real estate price... but I digress...
My advice? Keep her home if you oppose the test. The school will likely give you a hard time if you send her and they really are not obligated to provide alternative programming for her while the rest of the class writes the test.
EQAO is totally different then the gifted screening. EQAO's purpose is to gather information for a variety of purposes, which would take way too long to get into right now. Here is their mandate link:
http://www.eqao.com/AboutEQAO/01about.aspx?Lang=E
Gifted testing, at least in my board, is done in Grade Three and screens learners for a variety of academic gifts that may be better served in a community classroom with other gifted students. Parents who are not satisfied with their child's results (ie: think they are gifted and they were not selected) can have the child privately assessed by a certified psychologist and the board will accept the findings for placement.
Hope that helps!