I loved this movie. Tamera Mowry (Shelby) gave a great performance. As did Ronnie Rowe Jr who played her Boss (Evan). He reminded me of the Gretch, but unlike the Gretch, he wasn't heartless, just clueless about other people's feelings. However, as the movie went on we watch him come out of his Rocket Scientist Nerdy Shell and evolve into this sweet caring person. However, Evan being a rocket scientist was not the point of this movie, which is why they didn't focus on his occupation, but rather on his transformation. This is evident when Evan's boss explains that his work performance was not the problem, but it was his people skills that needed to improve.
Anyway, If you didn't see the plot of Gretch that stole Christmas in this movie, we weren't watching the same movie. At one point, during the Christmas party, I thought (Shelby) was going to say "his heart is growing"
The ending was so sweet and so prince charming.
Lastly, I agree that Isabel Birch (Grace) wasn't the right fit for this part. She seemed to be a little kid trying to (act) like a little kid. It didn't seem natural.