Yup, that's the thing about these self-appointed "Saint Ns". They make you feel bad for being suspicious of their actions until it becomes clear that you are indeed right, that their actions are based completely on their own selfish needs.
Reminds me of a comment my Nmom said to me awhile back. Our church sponsors charities several times a year, particularly at the holidays. At Christmas and Easter, our church has a program where you pick a "tag" with a child or needy family's name on it with a "wish" list of items they need or want. Parishioners pick a tag, buy items and wrap them and return them to the church for distribution. This small act of kindness is "anonymous", for obvious reasons. Children like to think that Santa or the Easter Bunny provided them gifts, not a Jane Doe. Also, the focus is on the person in need, not those doing the giving. I participate in these activities every year gladly and try to be very generous in my gift giving to these children or families. Once when wrapping up some of these gifts, my Nmom responded, "Aren't you going to sign your name to the tag?" I explained to her that I wasn't and the reason for it. She just shook her head and said, "Well, I wouldn't do it then. How will anyone know that you were the one giving the gifts?"
Obviously, she just doesn't get the concept. I also volunteer at my church as a catechist teaching 6gh grade students as well as other activities. Looking back, I realize now that I can't remember my Nmom, Nsis or co-dependent dad ever volunteering to help out with anything. My Nmom, being the materialistic and power-seeking person she is, will write a check to rare charities, but frankly, the money never comes out of her own pocket. She arranges to get her company to sponsor the charity and write the check. But she has never once volunteered her time or effort in any way to benefit someone else, especially someone she doesn't know. Kind of goes against the concept of being a "martyr" or "saint" doesn't it? When it comes down to it, they don't emulate saints in any way at all.
My Nsis, too, is even worse in this "martyr" department. She is the type that will flaunt her good luck in life by buying expensive gifts for her family (thankfully, neither my brother and I have nothing to do with her anymore and so aren't the recipients of these gifts any longer). However, in addition to pointing out how "rare" or "expensive" or "clever" these gifts are, she will keep a running tab comparing what she received in return. If it doesn't "add up" to the same amount she gave, she feels offended, slighted and wronged. My Nmom does the same. It's always a "tit for tat" situation. She will never buy a little gift for someone or engage in an act of kindness for someone unless she knows it will be returned. It is so opposite what both my brother and I believe.
I guess the truth is that Ns just don't possess giving hearts. They don't value or understand why it's important to give of yourself to others without the expectation that it will be returned. I think subconsciously, deep, deep down, a true N is terribly envious of those who very obviously have hearts and can express their generosity in human ways.