Perform a Kumbha Vivaha for the girl before actual marriage to the boy. Consult locally in your area for details.
Also perform a Rahu and Ketu Shanti before marriage. Turmeric abhishekha for Lord Laxminarasimha on a Swati Nakshatra day (also called Swati puja in some places) also helps to keep Rahu from doing harm.
Proper Sankalpa should be taken before any remedial measure.