Most definitely so. We have a saying especially for this situation: Доброму вору всё впору (literally: Everything fits a good thief). впору is synonymous with как раз
These days the word кофточка is widely used as a synonym of блузка (a blouse - in the sense of a woman's upper garment). Strictly speaking, though, кофточка is a diminutive form of кофта, which means "cardigan". To older generations of Russians, кофточка only means "a little cardigan" and never a blouse. The garment is knitted and open in front.
"The gray blouse fits her perfectly" was marked wrong. Is a кофточка not a blouse and therefore a generic phrase for any garment worn on the upper body other than a jacket or coat? Or is "fits her perfectly" somehow wrong? Everyone I know uses the expression "fits perfectly," not "fits just right." The latter sounds like a line from Goldilocks and the Three Bears.
can anyone provide me a translation so I can remember this structure? To me it just looks like "as once"
ей как раз literally means "to her, [it's] like 'bang!' [fits perfectly]". Apart from 'once', 'times', "раз" is used as an interjection similar to "Bang!" or "Wack!". The word is related to the verbs поразить (to strike) and сразить (to defeat by striking) and distantly related to рез- in резать (to cut).
Он/она/оно ей впору. Or Он/она/оно ей как раз. Speaking about a dress/suit/costume/jacket 'fits her' can also be translated as 'сидит на ней хорошо'
Is it only related to size or fit? What I mean to ask is if it could also refer to the color or cut suiting the person? I wrote, "The grey blouse is just right for her." and it was accepted.
Как раз / в пору only refers to the size. Speaking of color or cut, we would say, "Серая кофточка/блузка ей (очень) идёт" or we may say, "Серая кофточка ей к лицу". There is even a proverb "Молодцу всё к лицу" (=Everything suits a handsome guy).