The first BF went on vacation with the Yorks, and he said Beatrice had intended to present him to the Queen.
So it may have been quite serious, although she was only 17 at the time.
That's what he later said, because he couldn't be lying obviously, I really doubt he was ever going to meet the Queen even if she had said it. It was probably her first relationship when she was very young and got nowhere near in the same galaxy as her relationship with Dave or Edo. That said, even a bad relationship at that age teaches you something.
As for his ex fiancée, it makes me even more uncomfortable to be speculating on her reasons for becoming pregnant. She did and they were together for a while. It's probably a good thing they broke up at this stage rather than go through with a marriage but we'll never know the full story. Nor Beatrice's with Dave for that matter. They shouldn't rush especially because of the young kid but an engagement next year (if that's what they want) is a reasonable time frame.