Well, she'll have to actually find the alien first.
So what, the alien wins because it avoids combat entirely? Not much of a fight...
By that logic, she could win by just flying away.
Will she continue to fly indefinitely? I think that the alien has the advantage in stealth and close-combat while Reisen has the edge in artillery and ammunition. I fail to see any evidence that xenomorphs have eyes and/or ears. Alien 3 demonstrated some sort a visual sense, but that would be consistent with echo-location, pressure sensors, or radar to name a few. More so that sight if my recollection is correct and the xenovision lacked colours...
echo-location, and radar decidedly fall under "wavelengths" and thus are valid targets for manipulation. AFAIK, wavelengths don't give off appreciable pressure either.
Who gets the killing blow off first? That will be the winner. As far as killing blows go, at range the alien has none. Acid is relatively slow (compared to things like bullets), short range (ditto), and is likely to do more harm to the alien than good, by revealing itself.
As far as melee killing goes, the alien is superior, granted, but that means it has to get CLOSE.
Both sides are smart enough to realize that they have a nearly unstoppable advantage on their "home turf" and likely neither of them will leave it.
It will either end up as a tie (Because neither of them ended up forsaking their advantage and so no fighting ocurred) Or the one to forsake their advantage will likely lose. IMO the Alien forsaking it's advantage is in a significantly worse position than Reisen forsaking her position, but both are still pretty bad.