I will definitely need to see the DNA evidence to make up my mind on this one.
However, I'm a bit doubtful that Queen Victoria connived with Wilhelm to have the child married off in 1849 and sent to Australia. Admittedly, Wilhelm had spent part of 1848 in exile in Britain, having fled Prussia because of the 1848 Revolutions, so he and Victoria certainly knew one another. However, it was not until 1854-55 that the two royal families became close, with the plan for Wilhelm's son to marry Victoria's daughter. Plus, if you want to get an illegitimate child out of sight, out of mind, you don't wait until she's adult!
Ann