You can delete your Spendlify account, with everything in it, yourself. You do it from inside the app, on the website or in the Android app, and it happens straight away.
If you sign in with Google and have no password, the app asks you to have signed in within the last 15 minutes instead. If it has been longer, sign out, sign back in with Google, and start again.
Your account is deleted the moment you confirm. There is no waiting period and no undo. Every device signed in to it is signed out, and you land on the sign-in page. The app sends no email about any of this, because most accounts here have no email address on file.
Nothing is kept on purpose. Nothing is archived, hidden or held back in case you come back. For a short while after, copies still exist where nobody is reading them: in the server’s backups, for a few weeks, and your username in the server’s logs. The privacy page has the details.
Ask the person who runs this server to delete it for you. The privacy page says who they are and how to reach them. Tell them your username. They may ask you to show the account is yours before they delete it.