She's really bored and Peridot broke all the potential ways home.

She had a simple goal on fusing with Lapis again, but when that didn't work out she blamed it on Steven.

I don't really think she had any actual goal other than becoming Malachite at that point, because she was sure Lapis would say yes, so everything she's been doing in all episodes after that one is probably just to get revenge for her fusion plans to be stopped.

Jaspers are stubborn, but is not like they need a very complex or realistic goal. She wants to wreck the crystal gems now, so that's what she's doing. I mean if she really cared about going back to homework her priorities would be similar to peridot's: kidnap steven, force him to repair the warp to homeworld. But nah, she just wants to defeat "Rose quartz" to prove that she's stronger on her own, now that her plan to be fused with Lapis failed.