A quick check of Missouri statutes on the state legislature's website indicates that the section you refer to was repealed in 2009. You can see for yourself at this link: http://www.moga.mo.gov/statutes/c452.htm
Generally speaking, the judges hearning family law and paternity law cases understand the rules applicable to child support, child custody and other related matters quite well. If the court heard the matter and made the changes you indicate, then there is likely nothing your neice can do other than bring another motion to modify if circumstance change significantly.
Of course, you are always free to take your case to another attorney at any time if you lose confidence in your present attorney.