To give some background, just as we were getting together my girlfriends parents divorce finally came through. My girlfriend recently mentioned that when we got together her mother felt lonely and that I was taking her away. I get on really well with her father (we have a lot of shared interests) and have stayed with him many times while visiting my girlfriend but because there isn't really space at her mothers I have only met her a couple of times. On both those occassions I felt really awkward and found the atmosphere quite tense.
It doesn't help the situation that her mother didn't initially react very well to the fact that her daughter is with another woman and behaved in my mind quite badly towards my gilfriend along the lines of I don't know who you are anymore. My girlfriend knows that I don't feel altogether comfortable around her mother and I want to make the situation better because I know this makes her unhappy especially because she is much closer emotionally to her mother than her father (SAHM v.s. father working long hours with lots of travel). Would I be unreasonable to go over with her to visit her mother for a meal when I next go up to visit her at her dads (they live a 10 minute walk away from each other while I live two hours away) given that the divorce was very messy and it might upset her father who I currently have a great relationship with.