Here are two mainstream news articles. The first link details the times Sarah was last contacted. The second is a search that was called off for a possible jumper right in the area where Sarah's car was found (on Route 35 Belmar Bridge by Shark River). This may be a coincidence, or the police may have thought Sarah was a jumper.
IMO I don't believe Sarah jumped the bridge. As shown in the third link to her Twitter page, her recent tweets do not indicate any of the usual suicide warning signs, including her likes (saying goodbye, liking depressing posts, talking about leaving, etc.). In fact her last tweets express her excitement to see friends and family. One of her last messages was about being excited to see someone in Toronto, which she is known to have visited often. This does not sugggest to me that she committed suicide, this suggests she was taken, or something happened to her against her will.
I attached two pictures from google maps that show the area she was last seen. It shows Neptune City, where she is from, and it shows Belmar and the Route 35 bridge which I put an arrow next to (the arrow does not indicate the exact location of her car, it is just showing the Route 35).