If someone around has the rulebook, please post the relevant part of the rule.
If memory serves, the runner cannot be put out between the two bases where she's obstructed, but must still run the bases legally. The LBR, to me, is exactly like the other exceptions you mention. Change the sitch just a bit, making it just minor obstruction (say BR merely had to run around F4 - but no contact), have BR run a couple more steps toward 2nd, and then stop a 2nd time. Do you have an out now, despite the OBS? And if you do, why here and not in the original sitch 2?
I debate all this strictly by the book.
However, if I was in the sitch, I suspect I'd find some way to protect this runner, as I suspect most of us would (God Rule perhaps). But BY THE BOOK, I believe an out is the correct call.
I await the responses of those smarter than I (yeah, that's most of you!
)