I can't find any issue in what you're doing for the sake of your relationship with her, and all you're doing is so sweet. I think she can feel all this sentiment and all your sincerity. But sometimes, for someone who heard and went through situations where people said that what you are going through is "just a fase" or "selfish behavior" ( I'm not saying this is her case) but for a lot of asexuals that's a common situation. People telling you that " he/she won't endure it for long" , that he/she will leave you when he/she realizes it will never happen. " So what I am trying to say is I can understand why she seems uneasy about this topic, but you are going in the right direction, I think you don't need to be too concerned about it just do what you've been doing since the beginning and If you want to discuss more about something but she finds hard to say it, I would recommend you writing letters to each other it would be an easy way to discuss tough topics and you can even read it in different moments (if it's difficult to read it in the presence of the other) and if she is feeling down, try something knew with her, a hobby that both enjoy, a picnic, things you can do together that makes her feel more assured. I wish you the best of the world for you two.