You might want to make contact with this guy...
http://forums.b2evolution.net/viewtopic.php?t=13253

I don't see any problem with Russian there. Try to change the encoding in your browser to Windows-cp1251

I dont see ?????????? because my FF has default language [ru] in settings.

But I do see ????? in IE with default language [en]

If you use both En and Ru in your blog it's probably better to move it in UTF-8.

Try to add this string in _html_header.inc.php file in her skin folder

<meta http-equiv="Content-Type" content="text/html; charset=windows-1251" />

If you don't see this file there, just copy it from /skins/ to /skins/your_skin/ and put the code in.

Appreciate the help. Its not the browser encoding, I've tried that MANY times (to the point of insanity, trying the same thing over and over hoping for a different result).

If fact, if she simply logs out, the screen changes to unreadable. Any account with a preferred locale of Russian cp1251 (RU) works fine though, and can read the English posts as well without problem.

Basically, whatever the format its posted in, the preferred locale of the reader must match (and therefore the reader must be logged in). I've toggled this between Russian RU and Russian cp1251 (RU) to convince myself of this.

However, setting the Global Default Regional preference does NOT make this function for a non-logged in viewer.

As a temporary work-around, I've created a minimally privileged Guest account with that setting, and taglined on her blog "Login as Guest to read this Blog".

FWIW - the mysql database backend uses UTF-8

1. You should set the default locale for Russian blog.
Backoffice->Blog Settings->Main Locale:Russian cp1251.

2. Add this string in _html_header.inc.php file in her skin folder

<meta http-equiv="Content-Type" content="text/html; charset=windows-1251" />

If this doesn't help we need to configure your b2evo to use UTF-8 in transactions and change Ru-ru cp1251 to Ru-ru, but I think that two steps will fix it.