Yes that is possible. If you are using sharedUserId imagine that those 2 applications run in the same thread which it means they have the same application life cycle which basically means that with the "force close" on any of these applications you terminate their thread.
Meaning that everything on this thread is killed. One of the negative things in using sharedUserID and sharedProcess between applications rather than using content providers.
I don't think there is a work around when you are force closing the app. Maybe you should just finish it the "normal" way and let the os kill it.
UPDATE from your comment:
In general I don't tend to intervene with these kind of stuff. The user might want to manually close the app, as I am used to doing, and it would be irritating if you have a service or the app running again and again.
That's my point of view. Despite my belief, there is a trick to manually relaunch your application after force closing when an unhandled exception had fired and I guess the reaction of the force close by user would be the same. You could add the pending intent in the service I guess: Android: How to auto-restart application after it's been "force closed"?