I talked to a trusted colleague tonight about this situation (someone who is "peer" to me) and whether he thought I should go to HR and his immediate response was: "Don't you know about what happened 3 years ago?!" I did not. Apparently, the department tried to fire her (for reasons I'm not entirely clear on) and she went to HR and claimed the department was mistreating her-- she made friends with the HR lady-- and she ultimately won the case. Now, she regularly has the HR lady over for dinner. In fact, I've heard her talk about "first name" but I did not make the connection that she was the "HR lady." Presumably, there is an entire HR department but, from what I understand, this woman is in a senior/important position. So, clearly, my colleague does NOT think I should go to HR. My colleague thinks I should be direct, be cold, and avoid her-- but not involve HR. He also said that, when possible, he would "rescue" me if he saw her cornering me at work. So, at least I have some back-up-- but it definitely feels as if there is no one safe in an authoritative position for me to go to. I can still document what happens, but I would not give that documentation to anyone unless a situation occurred that absolutely demanded it.

ETA: My trusted colleague also confirmed that he has heard me say "do not touch me" to her at work and witnessed her continue to touch me after that. So at least someone else at work has witnessed it-- if it comes to that.