My 2 Ds who were waitlisted at their top choice schools just moved on. The schools didn’t show them the love so they returned it. 
The entering class of 2017 was overenrolled by over 300 students. This created a housing crunch on campus. No students were accepted off the waitlist in 2017. In 2018 Northeastern took a conservative approach to acceptances and they did go to the waitlist as @ProfessorPlum168 stated.
just to give the OP advanced warning, assuming you have accepted their offer to be put on a waitlist and have sent some communication regarding interest, there won’t be any more uninitiated communication until the end of April email which I mentioned above. Some schools that put you on waitlist will send you COA breakdowns, but not NEU. You are assigned an admissions officer though so feel free to ask him or her any questions in the meantime. They are very responsive from my experience.
My advice – love the ones that love you!
Doesn’t hurt to send any updates and continued expression of interest, but don’t bank on it. Let it sting for a couple days, let the other news come in, and then start making decisions based on the schools in hand. Accepted student visit weekends in April really turn the tables on the dynamic – at that point, the schools are trying to sell you on their institutions and woo you into coming. Your D will wield the power then!
Update – DD just came off the BU waitlist! Now to decide…