Your privacy is your own and Romantimatic does nothing to change that.
The app will ask for access to your Contacts, but only to allow you to select your sweetheart; it does nothing with any of the other data. It sends messages via the normal processes (either SMS or iMessages), meaning that your sweet nothings will only be sent to who you intend. Neither will the app ever send a message without your permission. Any custom messages you create are stored on your device and only your device, and are only sent to who you decide to send them to.
Romantimatic does collect data about any crashes it experiences and delivers them to Extra Moon LLC, the makers of the app, but this process is totally anonymous and only used for debugging purposes.
If you have any questions about privacy for Romantimatic, please contact us at firstname.lastname@example.org.