This might be a bit unusual, as I'm looking for a web original story (unpublished, possibly even not finished, available freely somewhere on the internet).
From what I remember the main character was a Japanese girl (author flirted with magical girls tropes) in an approximation of current world who gained... well, magical powers. She was able to create portals. She had some kind of helper that was teaching her how to do so effectively, standardised usage - this maybe happened in a pocket dimension? There were other magical worlds, with elves and other creatures, there was a multi-dimensional power-play in the background...
Everything was sprinkled with scientific authenticity and thought - at one point her attack was using the pressure at the Mariana Trench, much thought was given to what the portals are actually stationary to etc.
Work was unfinished when I was reading it a year or two ago, and almost definitely is not older than 2010.