In our timeline the Tay Bridge: https://en.wikipedia.org/wiki/Tay_Rail_Bridge , was built over the Firth of Tay. Shortly after its construction Queen Victoria traveled on it on June 20th, and then on December 28th it collapsed in high winds, killing 75 people.
Lets say that a combination of these factors occur:
1.The Queen is delayed in visiting the bridge and comes a few months later.
2.One of the many construction flaws is slightly more problematic than OTL.
3.High winds occur while the Queen is on the bridge.
Due to these factors the bridge fails killing the Queen and anyone traveling with her, sometime between June and December of 1879.
Lets say that a combination of these factors occur:
1.The Queen is delayed in visiting the bridge and comes a few months later.
2.One of the many construction flaws is slightly more problematic than OTL.
3.High winds occur while the Queen is on the bridge.
Due to these factors the bridge fails killing the Queen and anyone traveling with her, sometime between June and December of 1879.