Firstly, I'm an avid watcher of these types of Christmas movies. I watch one-two during the daytime leading up to Christmas Eve. I like the feel-good simple romantic comedy spirit about them.
With that said... While the plot for A Merry Single Christmas seemed Christmas-y entertaining and right up my alley, between the writing (that is, the dialog) and the acting, this is completely unwatchable. I have seen better acting at high school plays. There's only one scene that was worth anything: The last scene of Juliet's, which isn't even the lead character.
I strongly suggest not wasting your time. You will want that one hour and twenty-eight minutes back...just like I do.