From this site:
"An owner of a servient tenement may try to claim that an easement has been extinguished because the dominant tenement has abandoned the easement. Usually, lack of use does not amount to abandonment and the right to use the easement will remain even if it has not been used for a very long time.
To claim abandonment, the servient tenement must show that the owner of the dominant tenement has done something that positively signifies his abandonment of the easement. For example, if a dominant owner bricks up a gateway, or blocks off the gateway by building a house extension across it, so as to prevent its own access onto a footpath or drive over which he enjoys a right of way, then the servient owner might assume that the right of way has been abandoned. The servient owner might then be able to act as if the right of way had been extinguished, for example, by planting across the right of way or by building an extension across it."
YOU HAVE NO RIGHTS TO SOLE USE OF THE PASSAGE WAY - END OF.
Not with 100 locks, 50 gates, etc. Only if SHE had blocked the 'easement' could you have a hope of claiming that she abandoned it.
She hasn't asserted her rights (as yet) to access since you lived there, but you haven't been in possession of the shared access more than 10 years, so can't even claim "squatters rights".
In addition, the fact that she has taken no measures to provide electricity is of no consequence. Presumably she didn't feel that the passage way needed electricity, and the fact that you took it upon yourself to provide it is your look out.
It would be crazy to suggest that if I chose to replace a fence on a boundary when it was actually my neighbour's boundary, the boundary would become mine, wouldn't it?
That is the flawed logic you are applying to your case.
I for one feel very sorry for any future clients you consult once you are qualified, if you can be this slap-dash with your application of the Law to your own affairs.