I'll add, Longwood Christmas has a whole different look at night than during the day. If you go and you love it, a second visit with the sun up or down could be in order.

Also, Reading Terminal Market is a great place to eat, and maybe buy some treats to bring home from friends or family. It's generally so busy nobody is going to notice you are alone. It's nice and warm in winter, and big enough to walk around for an hour or so.