Between 1910 and 1930, according to SP, there were 20 Dunlop children registered with Wilson as a middle name. However none of those had a first name beginning with either C or K. So Catherine must have acquired the middle name after her birth was registered. Or, perhaps, if she had two middle names, there isn't room for the second one (Wilson) in the online index.
There were 21 Cath* Dunlops registered in 1920-1922, 4 of whom were registered in 1921. One of them was registered in Fauldhouse, West Lothian. The registration does not include a middle name starting with M.
It is quite probable that the tree on A*****y is correct, but it may not be; you cannot trust any information you find in an online tree. Use it as a pointer to finding the original documentation.
The only way you are going to make real progress is by getting the information in that 1943 marriage certificate. As it is less than 75 years ago, you cannot view it online. You can either order a copy through the SP web site (quick, reliable, and you have to pay for it), or you can appeal for someone who is going to the SP centre to look at it and transcribe the details for you (free, unreliable, maybe slow). Or you can wait until the 1943 marriages are made available online in 2019.
