No, a TA in the US cannot book through the UK site. Either your friend misunderstood the TA or the TA is giving her false info. Package rates for 2016 haven't even been released yet, so one could only estimate what the dining plans will cost in 2016. In fact, you can't even book a 2016 package right now. Aside from that, booking early doesn't guarantee ANY discount, nor can you stack discounts even if they are released. And you can't book dining for Dec. 2016 in Jan. 2016.