よかった(良かった) Past form of よい which is another form of いい which means good
わかったわ=わ is a feminine ending that girls add sometimes to sound more womanly (is this what you were talking about?).
わかったが (分かった)=I understand but...が(stiff sounding)=けど(colloquial)=けれど(written style/formal)=but
わかった=understood/I understand.
http://www.polarcloud.com/rikaichandownload this(firefox addon) then go to tools->rikaichan to enable. Now mouse over some Japanese text (also, press shift after you mouse over a word).
This post was edited by Window on Jun 9 2009 10:10pm