There are few events sadder for a congregation than to lose members, and this includes those who are moving on in life as well as those who have passed on. They often see it as a lessening of their community, but this does not mean they will try to hold those who seek other ways to worship. Even though they generally state their way is the only way, many people in any faith realize there are a variety of ways to worship.
Leaving the community of any church is generally pretty easy, and most people simply stop attending worship services. Even modern churches are not heavily dependent on paperwork, so the door is always open for a former parishioner to return. The church might simply consider them lapsed in their attendance, and rejoining at a later date is generally permitted with no obstacles to navigate. There are a few churches that might require a person go through a baptism or other religious ritual, but most accept their former members back with open arms.