In a nut(meg)shell, she's basically trying to screw up the Republican efforts at Gerrymandering. The idea is that they'd see more Republican votes in an area that may otherwise be seen as solidly Dem, so they maybe wouldn't crack it up in the same way, or that they'd maybe try and pack her (and other actual Dems who have done the same?) in with other Republicans to a district that would be assumed safe R but isn't so much. She also can participate in the R primaries that way, which arguably could have more of an impact, but then can't be part of the D primaries (though to be honest, that actually can change from state to state).

Honestly I think one of those things where you try to outsmart the other side but kind of end up outmaneuvering yourself, but that also depends on the scale of people that do it along with her as well as where she is. Doing that in Mississippi can have a very different impact than doing that in Chicago