Let me see if I got this straight:
You are in love with HER, but you are married to her.
Can't live without HER, because it hurts all the time, but you are still married to her.
Your families and her opinion still mean more to you the your feelings for HER.
Question for you to think about if you would:
How long before you and Marla stop having coffee and start having each other for lunch to cure the ache?
It is a poor excuse to use other people to justify your desires to end a relationship you might not want to be in any longer.
Get Divorced, and Get Help
Get divorced if you've got to, but don't use HER as the excuse if you do. I suggest that you seek out professional help first to sort out the feelings before you do anything that will have a lasting result in your life.
What do you think of Survivor's Answer?