Johnny13x,
When used properly, birth control pills are 99.9% effective in preventing conception. However, the young lady has to remember to take them everyday.
Male condoms, when used properly, are stated as being 98% effective in preventing pregnancy.
However, when speaking of preventing the transmission of diseases, then condoms need to be used to reduces the possibility of infections. No method is 100% effective at this, but condoms are the best available (besides abstinence). Birth control pills do nothing in preventing transmission of STDs.
So, if the birth control pills are taken properly, the addition of condoms does not help increase the effectiveness. But, condoms do help decrease the spread of infections.
Good luck.