As of the time of the series, Eri is working full-time, presumably at her own practice. Lawyers work notoriously long and stressful hours, and it's not unheard of that they abuse amphetamines just to make it through the day. While I highly doubt that last bit applies to Eri, taking care of Ran in the manner expected of a diligent mother is something that would've detracted immensely from her career. Therefore, she probably let Kogoro deal with that, seeing as he evidently had a lot more free time on his hands.
It should be noted that Kogoro and Eri are legally separated and not divorced.
(Also, there's a designated thread for asking questions. Next time you want to know something you should do this there instead of making an entirely new thread.)
"I know that some unkind declarations were made, of rash vows and unspeakable things"
"But don't you know? When the rain lets up, you'll find that we belong to each other still."
"Apologies? What is that between us? Words cannot bridge what words could not break."
"Let's wipe the gunk off our clothes, the warm trails from our cheeks, and smile once again."