I do not have slicks on my MTB commuter, yet, but judging from your post, I think any of the choices offer a good value.

If you want more opinions on them, at least the Kendas are available on Amazon, and other people have reviewed them. The Fortes might be Performance Bike only.

Also, I wouldn't be too fixated on high pressure. Old rigid MTBs (like mine) are, well, rigid compared to road bikes.

One last thing. How wide are her rims? Many newer MTB rims are plenty narrow, but mine (from early 90's) are 1.5" wide. I don't know if a 1.5" tire would work for me, but definitely not anything narrower. I'm looking at 1.6" and up, and have a lot more selection closer to 2"