This is a great discovery, it must be very exciting and certainly liberating to have someone who shares a similar interest in your circle of friends. It is not always easy to find the right audience to express our feelings on the ABDL lifestyle. When we meet someone, or find out about someone, who may share these thoughts and feelings we can sometimes grab on tight with two hands and want to experience everything all at once. It can lead to some beautiful moments and allow us to be free of the stigma that society throws on us. Finding another to share with makes it OK to be ourselves and we can allow the troubles to fall away with ease.
From reading your posts, I can sense that you are very happy to discuss your needs and are trying to show your friend there may be more to being a little through trying diapers. This is fine, we learn through experience and experimentation what our needs and desires are. It is not enough to simply imagination or fantasise, we have to touch, feel, hear and indulge our thoughts through real-life experiences. The one thing you must not do is use any force or overly persuasive techniques to get your friend to try diapers. It sounds, from what you have explained so far, that there is a slight piqued interest. That is great and it allows you to discuss your own desires about wearing diapers in a safe environment.
When we want something very much we can become jaded in what is acceptable. We may find ourselves inadvertently forcing our desires on others and it can lead to hurting people. You have taken a bold step by opening up to each other, now you must take a step back, reflect and ponder. If when you next speak about your age-play and diaper needs you both decide to indulge each other then that is excellent. Just do not get disappointed if she decides to just age-play without diapers because it is not for everyone who identifies on the ABDL spectrum. It may be that you want to ask if she is happy for you to wear around her perhaps? If then she does discover she would like to try you will be a position to help that, but for now I would stop any notion of convincing her to go any further than she has.
To further my point here, if one of my friends also enjoys eating a burger it does not mean we both have to eat the same one. Just because you and your friend share a common interest it does not mean you have to experience it together. You can remain friends and chat about what you get up to without actually having to do anything with each other.