If she has already been using in her own tank and I think she's being a little bit too cautious. it's nice that she actually cares enough to actually suggest this but I don't actually think it's necessary to soak it fall that's amount of time. Do you know if it was properly prepared bogwood in the first place? I would soak it for three or four days just to get with any muck that might be on there. one word of warning, it may stain your water, it depends how long she's had it for. When you get bogwood for the first time, it normally does change the color of your water slightly but this is quite normal and won't affect the fish. Another thing to bear in mind is bogwood will have an effect on your pH, it will probably lower it over a period of time, so check every now and then.