Yes, after your both your suggestions I decided to put in a request to see whether someone would be able to help with searching the Huntly Kirk Sessions for mention of Helen Milne's birth on the "Lookups Request Board" (I'm in Australia so getting a chance to do this myself is not possible). From some of the response it appears as it may not be so easy??
I would offer but I live 300 km from Edinburgh and I don't know when I will next be able to get to the National Archives.
I wouldn't say it was difficult, just potentially rather time-consuming, and it requires a visit to Edinburgh or to one of the archives that has access to the 'Virtual Volumes' which are the digitised versions of various documents held in the National Archives.
You'd need to find and open the Huntly KS minutes and start reading through them from say the beginning of 1851, because the KS minutes are not indexed. Many, but not all, include the topic of discussion in the margin, which helps to find relevant items, but I do not know whether the Huntly ones do this.
You need to keep going until you find the relevant item, or until about 1860, because sometimes it takes the KS quite a while to catch up with errant parents. As has been said on the other thread, if both parties belonged to a denomination other than the Church of Scotland, the C of S KS would not get involved. So it can be quite a long job, and I suspect that those who are familiar with the task would be hesitant to commit themselves.
One way to tackle it would be to hire a professional searcher to find the information for you. This would cost a bit, but a lot less than travelling from Australia, and you would be sure of getting it done. There are links to lists of professional searchers on the NRS web site
http://nrscotland.gov.uk/