Unfortunately, the answer is probably no, unless you "hand-wave" the actual cause like you hand-wave the existence of the giants themselves.
Hypopituitarism is "almost certainly" the only type of dwarfism that would get you close to what you're describing. There may be some other, extraordinarily rare, types that come closer, but it's certainly the most common type that comes anywhere close.
All other (relatively common) types of dwarfism would cause other side effects that would make her distinctly not a 'normal' adult human, such as impaired mental capacity and delayed physical maturity (in other words, she'd look and act like an absurdly tall child, not passable as adult, even if the height, alone, were not an issue).
In humans, an average female is about 5 foot 3 inches (it varies from place to place, and with accuracy of measurement, etc., but this number should be close enough to accurate to make my point). The average human female with Hypopituitarism is 4 foot 3 inches. If you scale up that difference, and an average giant is 9 feet, then a giant with Hypopituitarism would average about 7 foot 2 inches. While I'm sure there are normal human females in that height range, they are the exceptions, not the rule, and your giant would definitely "stand out" in any crowd, just like those exceptionally tall human females do.
If you do the math in the other direction, and assume that this "dwarf giant" is average human female height of 5 foot 3 inches, and then scale up to normal height for your giant, the average giant female would be only about 6 foot 6 inches tall. In those ranges, any giant on the shorter end of normal could pass for a normal human on the taller end of normal, so a dwarf giant being able to mix in with humans wouldn't be anything really exceptional, she'd just be able to do it better than most other giants
Either this condition she has is absurdly rare,
or it doesn't correlate to any known human condition at all and is a specific issue among the giants themselves,
or it just plain won't work at all
Handwave the cause, and don't base it on humans, if you're going to do it. If giants exist, their own unique form of dwarfism could also exist.