Is she a plumber or a homeowner? The problem with the trap arm drop is that that the trop could siphon. It will boy siphon if the arm is straight, and that's what a plumber must do. From a practical standpoint, does it actually siphon out, and if so, how often? It sounds like she's never experienced this, and it might be difficult to eliminate the drop. That's all I'll say on that.
On the other hand, I have had a problem with venting below the flood rim. I was working on a drain for a kitchen sink. When we took the pipe down, it was full of grease 100%. But the tenant never had a problem. Where did the water go? Obviously it was draining in the vent, and we never knew to snake the line. Does this matter? I think it does for many reasons, among them, if the vent clogs, what if there is no access to snake it?