There certainly could be a connection, but I am not sure what it might be.
My gg grandfather was William Maguire, and he was born in 1789 in Brownstown, Cty. Westmeath, which is about 15 miles from Collinstown and a little farther from Mullingar.I assume that your Margaret was born around 1830.That would make my William an old father, but it is possible.He and his wife Mary Maguire had left the Westmeath/Meath area by 1830, however, and they had their son, William, in Dublin in 1825.They were in Canada by around 1830.
Since both my gg grandfather and my gg grandmother were Maguires from Meath/Westmeath, it seems likely that your William Maguire and your Margaret Maguire Fagan are related to my line somehow.My Mary had a sister named Margaret Maguire who was born on 19 Nov 1792 in Saraghstown, which is near Clonmellon.
Your William must have been born by no later than 1810 or so.That would mean that his father must have been born by no later than 1790 or so.My William had a brother John born in 1791, and my Mary had a brother Thomas born in 1795.Neither seem likely, but it is possible.
Thanks for responding, and please keep me posted if you learn anymore about your line.