My sister wants to start her own blog, but she doesn't believe me when I tell her she doesn't have to be a super scientist/math nerd/geek to do this... she thinks it's all coding and basically what The Matrix looks like on a screen... Am I right in saying that she doesn't need to know anything like this, especially using WordPress?
You're totally right! Making new sites in general isn't such an easy thing but everything depends on which certain type you need. And in case of blogging together with many other types of sites you really don't need to be a professional web designer or a programmer because there a lot of simple tools for web building which are convinient even for total newbies
WordPress is the best choice in this case, also Wix and Weebly. The last one isn't free but very cheap in case of price so can be a nice decision for making a separate blog too. All of them have very simple interface for using and there are also really many nice tutorials about working with them, personally I had very positive experience with WordPress and I've never planned to become a cool web designer
Even making a nice design with all that platforms isn't such a problem. Web templates are often recommended by experienced web builders for newbies and they're a cool alternative to expensive custom-designed sites. It's not a problem to find a wordpress design website with many types of templates as also in case of other platforms, some of them can be used for free too. Like in case of platforms they're ready design skeletons which are simple for changing according to your needs and tastes and again, no special skills are necessary here.
Also blogs can be made on the basis of such resources as Tumbler for example, it's even easier than in case of WorPress.