You should qualify your statement if the legs are covered as per Islamic dress code then there is nothing wrong with wearing Skirt. If the legs are exposed then it is very distasteful on the part of a Muslim woman.
No matter how modern or how liberal or how enlightened a Muslim is , it cannot be proven that Islam allows exposing legs like that.
I could take Hijab or no hijab as a grey area as per various interpretation of Islamic dress code. But none of those interpretations can prove that exposing legs like that in Public is allowable for a Muslim woman.