Yes, you are the only one who has access to photos. Other users will see only the photos you have emailed through and that's it. No one will have access to the library on your computer. However, if you have the photos stored on an online account, then I recommend double checking the security settings for Share feature, because if they're share with public access, then anyone can see them. As long as the pictures are stored locally inside the app, you will be safe.