[BoomerSooner]

I would call obstruction on this play as described because the OP expresses the judgement that the fielder's position cause the runner to have to alter her path.

That said, there is an element of judgement to this call without contact between the runner and fielder, which makes it possible that there isn't obstruction on this play. I realize contact isn't required to make the call, but without contact we have to consider the runner's path and the fielder's actions. I've always looked at it how imminent contact is based on the fielder's actions if the runner continues on the same path. In other words, if F6 has her back to the runner, is completely stationary and in the runner's path to 3rd, then I'm giving the runner the benefit of the doubt if she has to alter her path to get to 3rd base. Conversely, if F6 is moving into position to field a potentially thrown ball (read as not immediately in the act of receiving a throw) from the outfield and cuts across the path of the runner who then alters her path in some way, I've got to determine how necessary it was for her to alter her path.

Again in the situation from the OP, I'm deferring to the judgement of the umpire that was there and my interpretation is that obstruction is the OP's assessment. In general, though, the runner altering her path like this doesn't automatically lead to an obstruction call as I see it.