How to minimize onboarding steps for mobile apps when invited/added by another user?

Here's the best we have right now. It's 7 steps for UserB.
We use email address for usernames.
Can we do better?

  • UserA adds UserB, in app, via email address.

    1. UserB receives welcome email.
      Subject "UserA wants you to join them in AppName!"
      Body Button: "Click here to join UserA."
    2. Button in the email body links to web page.
    3. Web page asks for password then user clicks Submit.
    4. Web page sniffs OS and opens the correct app store on AppName.
    5. UserB installs the app.
    6. UserB logs into the app.
    7. UserB starts interacting with UserA.
Tags: