Agree with @elbrant and I'd like to add, when you return be very matter of fact, do not make a big fuss, particularly if she is excited and effusive in her greeting to you. Sure, acknowledge her if you must but don't make any sort of big deal out of it. Go about your business, e.g. if you've been shopping, put your things away before spending any time with her. Your goal is to make your absence just part of a normal routine, nothing to be excited about. I've had two separation anxiety dogs, and you know you have won the battle when the dog just glances at you in an "oh, you're back" way and doesn't bother getting off the couch! Yes, people like it when their dog greets them and makes a big fuss, but if you feed that behaviour you give too much emphasis to your absence and that can grow into anxiety in your dog.
Abbey goes to church
We live near two very large churches. One is a christian science church on a hill and with a lot of steep steps to go up. My Abbey, being very nosy, likes to go up all those steps when we are out walking and then sit down to watch the world go by. One Saturday when we were at Command Post Abbey there was a wedding taking place at the presbyterian church next door. When the wedding party came out of the church she wanted to watch the entire proceedings even the picture taking, and would not leave until the bride and groom got into the limo! Even then it was a challenge to get her leave. She likes to go to the presbyterian church–my church--in the evenings and wander through the garden and then sit on the front steps. Some dogs probably need to go to church but....