How different are Harley and Dr Harleen Quinzel?

I didn’t want it to be a complete body swap, there needs to be a connection between the two, but there are subtle differences.
[Harleen’s] not as outwardly crazy, but she’s still crazy in love and it’s making her act crazy - even though she’s trying to be rational about it all.
And the accent’s slightly more pulled back when she’s working in the asylum.

from SFX