The documentation says the one time activation fee is tied to your Google Play / Amazon / iTunes account, not to your Plex account. So it seems the answer is yes. That written, I’ve never seen anybody ask about it before, and I’ve never tried it myself, so cannot say with 100% certainty that it would work.
Unlocking or Activating Plex for Android
The purchase is tied to your app store account. You can download and use on any Android device with the app store you originally purchased it from with the app store account you purchased it with. For instance, if you purchase the app through Google Play, then the purchase will apply to any Android device using the same Google Play account. The purchase does not extend to a different Google Play account, nor does it extend to other app stores, such as Amazon or iTunes.
Make the second account as a free account, then add them as a Home user. They will inherit all of your (as the server owner) Plex Pass privileges, including app unlocking. No need to be friends/users for Google Store or anything like that.