Starfighter, what you're both saying is correct in a way. Neither of you are wrong.
Evolution is fact.
Evolution is also theory.
The problem, is that the English language uses theory in a different way. The whole problem would be solved of the word theory was replaced by the word explanation.
The explanation of evolution is the only thing we cannot fully explain. Theories are constantly evolving in order to include more info, but they are rarely significantly changed in meaning.
It's true that scientists use theory in a non-constant way, but it doesn't make it less factual.
For example, let's make a situation where there is a "theory of alphabet" which would say the alphabet is a series of symbols that represent sounds commonly found in english vocal range, and used to convey those words in a published format.
If one day we were able to convert letters into colors, the "theory of alphabet" might have to be altered to cover a non-publicated or audible format.
It doesn't mean the alphabet isn't there plain for anyone to see, it just means that there is more to explain "why" the alphabet is what it is.
Maybe a dull example, but the quickest I could think of off the top of my head.
For further reference, look up the evolving theory of gravity, with research done by a recent scientist that might alter the definition slightly in order to account for dark matter.
