I have a different take on this phrase. Calling a woman a bitch is normally an insult because the speaker is comparing the woman to a female dog (or "bitch"). However, many insults have been "reclaimed" or turned into compliments. Here are some examples.
"Queer" is an insult that applied to homosexual people. However, many homosexual people now use "queer" in a positive way. Example: "We're here. We're queer. Get used to it." "I'm proud to be queer." etc.
"Nigger" is an insult that applied to black people. However, many black people now use the word in a positive way. Example: "You're my nigga." (meaning: you are my close friend.) Important note: as a non-native English speaker, I strongly recommend that you do not use the word "nigger". It is often considered the most offensive word in the English language.
This use of a pejorative term in a new, positive way is called "reclaiming" the word.
Efforts have been made to "reclaim" the word "bitch." Some people choose to redefine B.I.T.C.H. as an acronym meaning "Babe In Total Control of Herself." In this case, "Babe" is a compliment, and someone who is in control of herself is someone who is worthy of respect. In this sense, being a B.I.T.C.H. is a good thing.
Even without turning "bitch" into an acronym, it has been reclaimed in other ways. Some people believe that a woman who is being aggressive, bossy or demanding is acting inappropriately and would call her a bitch. Other people may see the same behavior as assertive or confident and as setting a good example for other women. They may also call her a "bitch", but mean it as a compliment or as encouragement.
In this sense, a "classy bitch" can mean an assertive, confident woman who rejects traditional female standards of behavior but still conducts herself in a classy manner.
Please be aware that "classy bitch" is extremely informal speech. Many women would be shocked or insulted to be called a classy bitch.