Despite Madoka's "love" for Ryuunosuke, she wants to split his family apart which is just wicked selfishness with no regards to anything else. If she exposes Ryuunosuke's harekon familial situation to the media then this will just further prove the point as that may destroy his career.
Breaking up the family will also hurt an innocent child.
Madoka seems an unfortunate woman who go can't move on with life. I'm no psychologist but it also seems like she suffers from depression. Doesn't excuse her though for being a selfish bitch.