How much should I worry about my credit score?

Hello, My name is Ryan and I am new to BP and real estate investing. I having been doing a lot of reading and listening as I prepare to begin my investing career in Portland, OR. Our plan is to buy and hold while "house hacking" for a few years. I want to get involved as quickly as possible due to the appreciation run Portland is currently going through. I will be buying my first home with my fiancé who does not have the greatest of credit scores. My question is should we hold off getting preaproved to try to raise her score, or will her credit score not matter much if I cosign with a much better score in the 720 range? Any thoughts are appreciated. Thanks, Ryan