That's a fairly common arrangement. My first girlfriend and I had something similar, I could only wear around her if it was discrete and even then she wasn't completely on board with it and she didn't want to engage with me when I was diapered up and in baby mode, so I had to indulge on my own and in private. This wasn't a bad set up mind you, to me it said that she was accepting of it to an extent, she encouraged it as a part of my weekly routine, but she just didn't want to participate herself and that's totally cool, she could've been a jerk about it and declared it a hard limit, she could have made my being an AB a problem and called an end to the relationship right there, but she didn't. I guess what I'm trying to say is, if your current girlfriend let's you wear at all then that's a good thing whether she is an active part of or an accessory to your fetish or not. I'll also add in that I haven't had too much of a problem with finding willing partners, probably because I don't view my ABDL as a fetish thing, it's more of a lifestyle and form of stress relief for me.
I'll also echo some of the other sentiments shared here, it's very difficult to convert others to our fetish/lifestyle, probably because diapers aren't traditionally looked at as erotic, attractive or particularly interesting. I think the average person has a profound disconnect when it comes to diapers. If they are worn by an actual infant then they are seen as cute, but when worn by an adult I think people often think of geriatrics, incontinence and funny smells and most people don't want to be privy to that. Whatever the reason, diapers are a tough sell, so I'm not surprised that people who aren't normally into them have trouble wrapping their heads around diapers and ABDL.
I also agree with Slomo here, if having a fully accepting partner, someone who will both wear along side you and who allows you to wear out in the open is important to you, then maybe you should do some soul searching and consider if she is the one for you. Also, you gave it a shot, you tried to get her to wear and it just didn't take, from here on out it's best not to force the issue, really consider if you are content to wear on your own or if having a partner who also indulges is a must. I know personally I could have continued on with my girlfriend, the one who allowed me to wear and regress on my own time, but I personally find having a Mommy and Baby type dynamic in my life just makes things better, so we both called an end to things after 2 years and since then I have had another girlfriend and Mommy and my current Mommy friend and I've never been happier.
Best of luck to you