Who would win in a fight? Muscular Girl or Giantess?

"Normal" is the word I'm keying on here… assuming an "ordinary" girl suddenly* becoming much taller (but not heavier other than proportionally so… 10 ft., 220 lbs. still sounds like average starlet physique. (not familiar with the actress younamed, sorry, but I'm a little old to be the target audience for Dude, Where's My Car?  😀 Anyway, I'm thinking she's grown bigger but not really that much stronger, and not experienced in any sort of fighting techniques.

Whereas the muscle girl has trained for strength and flexibility to at least some degree, and while perhaps not formally trained in fighting either, is probably not shy about using what she's seen in the gym or on TV in a brawl.

I say the buffed girl wins.

*not necessarily instantaneously, but also perhaps over a period of hours, or days, which is still "suddenly" compared to normal growth.

The buff girl would easily overtake the giantess. She'd merely disrupt the giantess' center of gravity, bring her down and begin to wail on her. Once she's got her on the ground, the fight would end rather quickly.

In any battle there are far more factors to consider than merely someone's size, height and weight.
Example: do any of the girls have previous fighting experience, have either of them had combat training, are there physiques recent or inborn, who has the greater will to fight, are there weapons/items around, etc.
On basic mathematics, the buff lady would generally win because of the distrabution of her weight relative to the giantess' is lower and the giantess would become overbalanced trying to pick her up or grapple with her -just as Deadly Pixxie said. But the giantess could use the length of her limbs to keep the buff lady away and wear her down from a distance.
As said before, too many factors involved.
Peace
The Pimp NeonBlack

Depends, how tall is the giantess and how buff is buff girl? 
Ok, if buff girl is buff but still has her female figure then any giantess over say 20 feet could take her.  But if buff girl is fully buffed to the point where all you see is pure muscle, then any giantess up to maybe 40 feet could be in trouble.  However once you get above 40 feet the giantess would win.  this is only valid if the buff woman is average female height of around 5'1" to 5'6" and just buff, not tall.  How tall is the giantess?  I've seen some people put them up 5,000 feet high plus. I mean at that height no matter how buff you are, you're an ant on the ground. Don't make me bust out with my physics equations and do math.  I'll sick a giantess and buff girl on you for that. 
And in the end if you get to see both transform and burst through there clothes is that not all that really matters?
_M. Knight

I think your weight estimate is off for the giantess.  Remember that if you scale somebody up, they're not just growing in height, but also in width and depth.

A 10-foot person is 1.84 times the height of a 5 ft. 6 in. person.  But they'd also be 1.84 times as wide and 1.84 times as deep, or something.  I'm not sure this is the right calculation, but if you cube 1.84 you get 6.23, which might approximate the volume of the giantess.

So if that was right, then a 120 pound, 5'6" woman, scaled up to 10 feet (while still keeping the same proportions), weighs 747 pounds.  😮

P.S. I am a huge nerd