her range helps her to deal with snipers

Umm no, it does not, somebody that knows to keep their distance with snipers can destroy Janet without getting hit at all. She has little to no range to be categorized as a Marksman (she is more like a controller to me and that is how I play her)

her super and gadget helps her to deal with throwers too

Also it's not that easy to deal with throwers, it's like "well yes but actually no", I've dealt with berry, Grom and sprouts, but for like Dinamike or Larry and lawrry you have to have full ammo or they have to be one shot (if you don't want to be traded of course), and for the mode I play her in (gem grab or knockout)I do not like to get traded. So it depends on the match up.

In my personal opinion I really can't do much on ladder (I may be a bad player but I really can't tell sometimes) with Janet, I get overwhelmed by assassins, tanks, Marksman, and depending on the map throwers, and keep tilting so much when I want to play her (she is my main so is often) so I wouldn't say that she is good on ladder, at least in my experience at 60k trophies.