Technically, it really isn't a rescue situation. The lady is "getting rid of" the rabbit due to her allergies. Now, unless this lady was going to "set the rabbit free", then it would be considered a rescue situation. Your situation, as it seems, is a "rehome".
Why not schedule a day, with the lady who is "getting rid of" the rabbit, when you can go over there are meet the bunny and have time to see his personality before taking him home?
How far away is this rabbit from you? Would the lady who is rehoming the bun, meet you halfway?