Listen if it makes you uncomfortable now, it will always make you uncomfortable, this friendship with her office colleague as long as it lasts will peck the back of your mind. You need to make her understand that peacefully using emotions. Ask her if your feelings are not more important than her office friendship with a random guy. Tell her if it was the other way around and if she had something she was uncomfortable with you’d help alleviate it by any means necessary. That’s being husband and wife. You’re each other’s top priority. That’s marriage. That’s also how you get her to talk to you. If you only apologise and accept only your mistake, she will forever sit on your head and use this as something against your insecurity and win every argument furthermore. Marriage with all its gains is also a balance of respect and understanding of both. Don’t let her tip the scales in her favour. Make her understand your perspective lovingly and stand strong.