G19 all the way. It is one of the finest CCW pistols on the planet. Mine shoots like a full sized 9mm, yet disappears under a T-shirt.
(See what I did there?
Honestly, both are good guns. Both are relatively easy to conceal. A G26 isn't that much easier to conceal than a G19, especially if you use any of the different grip extensions (which basically give you the same size grip as a G19, just with a smaller sight radius, smaller slightly less accurate barrel, and fewer rounds).
I'd go with a G19, and a good IWB holster. If you can't conceal a G19, you'll have difficulty concealing a G26, and at that point, you might as well go for a single stack 9 of some kind.
EDIT: I didn't realize you are female. I still stick with what I said though. Glocks are big, bulky guns, and many females who don't want to dress like men all the time will have difficulty concealing them. A G19 is a little over .5 in taller, and a little under .5 in longer. That's really not that much difference in terms of concealment. It's huge in terms of handling and shooting. I really think some kind of single stack 9mm would be best, as far as concealment is concerned.