Maynooth is generally safe, especially for solo female travelers. The local people are typically friendly and approachable, and crime is relatively low. It's always wise, though, to mind your belongings to avoid opportunist thieves, and stay in well-lit and populated areas at night. The town is small and it's easy to get around, plus the local police are helpful. Public transportation can be relied upon and is generally safe to use. As always, take common precautions as you would traveling anywhere alone.