I've been noticeably emf-sensitive for over 2 years now (since the onset of this sensitivity, I have also developed some form/degree of MCS). I hate to be the bearer of bad news for your friend - but my experience with those free, cable-company-issued digital converter boxes have not been positive.
At some point in mid-2010, Comcast "went digital" - and made things such that it was mandatory that a digital converter box (it's technically called a digital-to-analog converter box, I believe) be installed to receive all of the basic cable channels that I had become accustomed to receiving. The company issued small-sized, seemingly cheaply-made digital converter boxes to hook up to the two TVs in our house that needed them (mine and my brother's). It's a good thing that I hesitated in hooking mine up, and that my brother hooked his up first - because on a "hunch" that these boxes might be bothersome - I went into my brother's bedroom to check things out, and felt a disturbing, symptom-provoking energy that filled the room. It didn't take much "detective work" to determine that it was the digital converter box that was emitting some type of strong, bothersome radiation.
My reaction was such that I never did hook up that digital converter box in my own room - especially since I was also being "zapped" by our AT&T WiFi router. Meanwhile, I had reason to believe that a "full-sized", official cable box (what you get when you want to receive more of the "expanded" cable channels and the subscription channels) would work better. Fortunately, I was eventually able to get such a cable box (Comcast has many different versions of this box - the box they gave me is perhaps their smallest version - but it is still more substantially-sized and more solidly-built than their cheap digital-to-analog converter box). Although the "official" cable box is not a perfect device from an emf-sensitivity standpoint (there are times when I "feel" it - or times when I turn off the box and notice a mild relief) - it is miles better than that digital converter box.
Of course, this is my own experience - there might be other types of digital converter boxes that aren't as bad. I wouldn't count on it, though. If your friend is anything like myself - it is quite possible that she is reacting to whatever is converting the digital signals to analog signals, or to the actual digital energy. That would be a factor with all DTA converters. On the other hand, there may be better-made DTA converters that shield you better from this energy.
Further evidence that I react poorly to (many) devices that generate/process digital signals is that my VCR/DVD-recorder has often been bothersome to me - a lot of my reaction seems to be caused by the energy it emits as its recording on the DVD side, or dubbing VHS-to-DVD, writing to disc and "finalizing" discs. But unlike my reaction to Comcast's DTA converter - which would have been constant because the converter is always "on" (even when the TV is off) - my reaction to the VCR/DVD ebbs and flows with usage, and it's easier to limit my use of the VCR/DVD player. It still would be nice if I were able to enjoy playing DVDs on it without feeling zapped. I may buy a smaller, simpler DVD player to use when I want to watch DVDs for an extended period - there is a good chance that that would be easier on my emf sensitivity than the larger VCR/DVD player.
Well anyway - I hate that I didn't have more positive and helpful feedback - but perhaps this is of some small use anyway. I wish your friend the best - believe me, I know the struggle.