Yeah there have been less dangerous plans, but you got to give her credit for two things. This time she's making sure she has something that can kill the big bad, and she didn't aid the big bad ultra-powerful, supposedly unbeatable enemy just to defeat him this time. Compared to her plans for Jack, this is an improvement.
Putting aside that Vriska has no idea what the "something" she's trying to find is, let's look at how this plan compares to her Jack-stunt, just for giggles. Doesn't aid the unbeatable enemy just to defeat him? She straight up said the key to defeating this guy who's destroying reality is to let him destroy reality a while longer, until she hopefully finds what she's looking for.
To clarify, when I said aid I meant more along the lines of making all of the destruction possible.
If Vriska hadn't manipul8d CD, DD wouldn't have found Dave's copy of the MEOW code. If she hadn't done that,
Dave would have burned it, Bec wouldn't have been made and Jack becoming omnipotent could not happen. Vriska knowingly and deliberately made herself a vital part of Jack's rise to omnipotence and rampage to make her victory over him all the greater.
She's not doing that with LE. LE's rampage is happening, and there's nothing that she (knowingly at least) did to cause it. What she's planning on doing is tricking him into destroying the parts of reality that will help her treasure hunt. He's already destroying the furthest ring in his quest to destroy Calliope, she's just making him destroy the parts that help her in her hunt. I don't know about you, but that isn't aid in my book. It would be aid if she was pointing him towards Calliope, not if she's just making him think she is. But you got me on the gathering ghosts to get him to blast the right parts of the ring, he would love to annihilate all copies of our heroes, and that would be aiding him in that. But it's not aiding him the way she aided Jack. She would just be making it easier for him to something he was already trying to do in order to get something she needs to destroy him. She made herself a vital part of Jack's rise to power, just so that she could beat him later and be epic. I don't know about you, but these are very different to me.
but as a kicker it guarantees the destruction of almost all sentience in the universe
I don't have much else to say, but this really depends on a lot of factors, like how big the furthest ring is (IRC, Feferi once said it was infinite, and she was raised by ole Glubby, whose proper spelling I can't be bothered to find right now, so she may or may not be a good source of info there), how much of it LE destroys before Vriska finds the weapon, how many ghosts are killed in the process compared how many ghosts there are, etc. And whether or not "sacrifice lots of ghosts" actually turns out to be the plan. It's just a possibility in her head right now.