Originally Posted by Skahtboi

Notice that just before the section that you refer to above, the NCAA rulebook also includes the following note:

If both players actions are appropriate to the situation and contact could not be avoided, it is inadvertant contact and neither interference nor obstruction.

To me, this places your question firmly in the realm of "judgement." Do you feel that the runner had time to "evaporate," as you put it? If so, then you would rule INT. If the runner, again in your judgement, did nothing intentional to interfere and had no time to alter her course, then your ruling would be inadvertant contact, which of course, has no penalty.

Does this help at all?

Originally Posted by CecilOne

Yes, that does help and is pertinent to the OP.