Worrying isn't always a rational thing. She may feel that being part of the first group is like being in a clinical trial but without the support. Personally, I doubt that will happen - these early users will be watched like hawks.
If it's the ten months v ten years idea then I don't take that one as seriously as some people do - most of those years are spent on pause, waiting for the next batch of funds, or the next hundred trial volunteers. Most actual complications/side effects are revealed soon after the vaccination.
What you can't see in trials are the rarities, the ones that happen 1:50000 cases etc - where some combination of genetics, pre-existing conditions, medications etc could mean some people react differently. They could monitor the current trial groups for the next ten years and they still won't see those - or for the next thirty if you want to see the affect on children born post-vaccination.
Personally, I can't do the next ten years locked in, so I'm in one of the clinical trials to try and help push the process along. We all have to decide where to draw the line.