It funny that you mention this. I feel like the whole idea of weaves make people think that its a way to avoid having to "deal" with your own hair. Weaves are usually longer than thicker and shinier than the original hair of the owners, so from a psychological standpoint, that woman with a weave then has the hair that she always wanted but never knew how to get. Many people dont want to put in the work to reap the benefits, they just want overnight success and thats where weaves come in. I used to be that girl who would have the flyest weave. My weave would be so perfect that people didnt even know that it wasnt my hair until I told them. However underneath was a hot mess. I didnt know anything about caring for my own hair, and in a society where the BSS sells every texture, color, and length, I didnt have to learn how to take care of my hair because I had the luscious weave of my dreams. I know this is long... however what im basically trying to say is that its not uncommon for a person to want to take care of the weave because it already looks good to them instead of investing in their own hair. Usually by the time a person gets to the point where they are religiously wearing a weave it been ingrained in their head that their own hair will never look like the weave no matter what they do. so in other words, I'm sure your friend sub consciously thinks that if her hair can never look as good as her weave, then why bother?
All you can do is try to open her up to the forum and give her some of your knowledge to see if she is ready to take the step in caring for her own hair, or at least caring for her hair while its underneath the weave. Remember this is very common, and alot of BW dont know that there are other options.