Ask her to mail you such an old document (as attachment), so you can see if the document really have gotten a password or it's just Word asking for passwords on documents without. That are different things, and they might need different solutions.
Also let her create a NEW document and send that to you.
My sister tried to use her Microsoft Word today and every existing file she tried to open (.doc) is asking for a password. She's only password protected one file on her computer and when she tries to use it, it still won't let her in. I have heard of this problem with other people, but have never had it happen to me, personally. I've done Google searches to try to find the remedy, but to no avail. Usually, I can get this all sorted out on my own, but this one really has me stumped. Any help would be greatly appreciated.