When any church or denomination teaches something as truth or doctrine which can be shown to be contrary to clear Biblical teaching or cannot be shown to be clearly supported by Scripture, then that is not a disputable matter.
There's nothing in the context of Revelation 12 that suggests that it's Mary although I can see that if someone comes up with a doctrine and wants to support it, they can and will find something somewhere in Scripture that seems to do the job.
The way that can be shown to be the case is when something is lifted out of context to support the doctrine and very loose interpretations and much rationalization is used to make it say what the person wants.
The Assumption affirms not sex but love. St. Thomas in his inquiry into the effects of love mentions ecstasy as one of them. In ecstasy one is “lifted out of his body”, an experience that poets and authors and orators have felt in a mild form when, in common parlance, “they were carried away by their subject.”…- See more at: http://www.ignitumtoday.com/2013/08/14/the-feast-of-the-assumption-and-fulton-sheen/#sthash.swNCCb5z.dpuf
If God exerts a gravitational pull on all souls, given the intense love of Our Lord for His Blessed Mother that descended and the intense love of Mary for her Lord that ascended, there is created a suspicion that love at this stage would be so great as “to pull the body with it.” Given further an immunity from Original Sin, there would not be in the body of Our Lady the dichotomy, tension, and opposition that exist in us between body and soul. If the distant moon moves all the surging tides of earth, then the love of Mary for Jesus and the love of Jesus for Mary should result in such an ecstasy as “to lift her out of this world”.
Love in its nature is an ascension in Christ and an assumption in Mary. (Sheen, 133, 134)