Maybe you’ve found yourself doing some of the following to try to help your friend:
Joining them in rituals, such as checking door locks
Constantly reassuring them when they’re anxious about something
Helping them avoid triggers
Through these kinds of accommodations, friends and families of those with OCD sometimes enable their disorder. This behavior won’t make their OCD better. You may actually intensify their symptoms. Let your friend know the ways you’ve been accommodating their OCD and tell them that you want to start decreasing your participation in rituals.