Here there is a verb which has not been mentioned previously, "aussehen" which means "to look like". Additionally, such combined verbs were not mentioned previously as well. For this reason anyone who reads "du siehst" will naturally translate is as "you see" and could not understand why "aus" is used in the end. Such combined verbs are an important feature of German grammar. Although the verb is combined like "aussehen, abgeben, etc" when you inflect them, they separate from each other and becomes ich sehe .... aus, du siehst ...... aus, etc. This important detail should be given before asking a sentence like that.
No, nothing wrong with that, Aussehen is a "Trennbare Verben" a separated verb, http://www.mein-deutschbuch.de/lernen.php?menu_id=30
yes, it's pretty strange to say things this way, but... that's it.
I can't speak for other forms of English, but you don't say "are looking" in that way in American English. You would just say "You look exactly like your mother" or if you really wanted to specify right now at this very moment, you'd say "You look exactly like your mother right now." or some variant of that.
You know people who are ESL will say really bizarre things like "You are just as like a one I once knew." It's a product of the sometimes different ways their language phrases things, we have to alter our habits and simply begin assigning new meanings at times to fully understand. I'm sorry that's not a "real" explanation but it's how I treat these seemingly strange bits.
Imagining the translation as being phrased in Olde English helps understand sometimes too,
trennbaren verbs are separable verbs in english. go to the link for details and you can find their list on internet. http://german.about.com/library/anfang/blanfang19.htm
ok here is a list of these verbs but you don't have to remember all of them. you will know them with practice http://german.about.com/library/verbs/blverb_pre02.htm