Interesting subject! I am a Christian who wears nappies without physical need. I will give my view...read if interested...otherwise don't!
My faith is an integral part of my life, but I am not a religious nut, nor a religious bore. I am quite liberal, curious and not one for following rules blindly. I tend to think about why I follow a moral or biblical principle and get to the core of its original intention and modern day application.
Frictions can arise between those who follow rules exactly and those who take the principle of the rule and apply this principle to the individual circumstance.
The first way runs the risk of being outdated and narrow minded. The other way can result in chaos with everyone having their own interpretation and twisting things to suit themself. In the middle somewhere, there is a responsible, relevant balance.
I think 'situation ethics' comes into this too. Situation ethics is generally considered as doing the most loving thing in the given circumstance, whether or not it fits the rules.
So, I have done much wrestling with my ideas of what God thinks about my nappy wearing habits. I am still working on this, but I firmly believe that above all, in the purest most loving way, God wants me to become the person he made me to be. I don't think God made me to be a nappy-wearer! But currently, I don't think he is against it either. To use a different example, I don't believe God made me to be a consumer of anti-depressant meds, but he made the medicinal rainforests, gave the doctors their brains and would want me to be healthy. Equally though, I believe there
are expectations he requires. It's not quite a 'do whatever makes you happy' scenario. A balance of love and lord. That's my beliefs.
I think that Christian people have won themselves two cringe-worthy stereotypes however from being flawed human beings and getting it wrong. Either they have been too accepting and seem like doormats, or they get judgemental and seem narrow-minded. No doubt some of them are, and I can only apologise on their behalf. But not all are like that.
On this forum we sometimes talk about managing to obtain self-acceptence of our less than socially normal desires or habits, to become resolved in who we are instead of conflicting with our own desires. It has taken me a long while to believe that God still accepts me in a nappy and he isn't shocked and he doesn't hate me. In actual fact, I have resolved some childhood problems through revisiting toddlerhood somewhat and as a result I am more the adult I was made to be, reaching my potential more and being less held back by anxiety, depression and other signs of inner turmoil.
I agree with some of the others that the girl in the thread-starting post is as likely or unlikely to be accepting of DL-ism as a non-Christian person. But the reasons they give might be different. I
understand abdl desires and it's taken me ages to work out that it's not necessarily 'God vs Diapers', although I like the snappy thread title!

A Christian person who doesn't understand the abdl nature
might still accept you as any other person
might but they may be doing so whilst also believing that God would not approve.
I suppose it may also be about using the diapers for sexual means. There is a perception that Christians are against sex. I really think God invented sex and he made people with a sexual aspect to them. I also think there is an emotional, psychological and spiritual side and I think that when people do sexual things together, they connect on these levels as well as on any physical level. I think they remain somewhat 'attached' in a non-physical way, so I think sex is way more significant than people sometimes realise and I want to only ever do that with one guy, who will soon be my husband, co-incidently! The drive behind this Christian view should be love, not judgement and legalism. Unfortunately, people know the 'rules' but not the ethos behind it, and Christians have this anti-sex stereotype. Shame really.
Any new girl/boyfriend without an understanding of DL-ism is going to have to work to be understanding, unless they are just a very laid back person! Having a faith-based viewpoint to consider is one reason why it might be more complex for a person to process the thought of a fetish. There are other reasons, as Dawes says, such as upbringing.
Anyway, that's my 2 cents worth plus some more spare change I had laying around!! I hope it works out well.