I would help her as I was able, but would excuse myself when it was time for the children's show, or if there was a backup of other patrons. "I'm sorry, but I'm scheduled to do X now/I need to check out some books for a while but will get back to you in a few minutes".
There's also nothing wrong with saying "I don't know how to do that myself - there's a library computer where you can look up a tutorial". And possibly later suggesting the library have a page with detailed instructions for each type of ebook.
In other words, be helpful, but not to the point of neglecting other patrons, or your other duties.
The Kindle is a bit of a grey area, because it is directly related to using the library. For things like filling out job applications, or using email, that really isn't in the library's job description, and offering services like that is more than a library is generally able to offer.
As an aside - I would say it's reasonable to expect a patron to know how to load books onto their eReader, and how to read them. I would not expect them to, on average, understand why you can't read a Nook formatted eBook on a Kindle, due to the combination of technical details, and the fact that the restriction exists solely for commercial reasons.