Have a look on the IGI and you will find that Margaret was born 29 Sep 1815 in Boleskine, Inverness, to Lachlan Mackay and Margaret Davis. Lachlan and Margaret had at least eight children including a son Huntly, born 20 Nov 1822 at Boleskine. There is no other Margaret born to a Lachlan at that time anywhere in Scotland.
Hope this helps.