get some root hormone, any type will do, liquid or the goopy stuff.
cut off a healthy branch, and cut it at a diagonal angle(45 degrees if you can). cutting it this way makes it easier for it to root, and gives it a greater area to grow roots out of. weed is stringy, and since it's green and wet it'll be hard to cut, so get something extremely sharp. make a nice clean solid quick cut, and put it in the root hormone right away. there should be instructions on the hormone package, depending on what it is, it'll have to be in the hormone for different amounts of time. usually it's something like 30 seconds to a minute for the liquid, and the goopy stuff you just leave on it. after you've got the root hormone on the bottom of your newly cut branch, put the branch in a root cube, and water it with RO water w/o nutes until it really roots in. this could be a couple days or a couple weeks depending on your setup. you don't want to over water, so just look at the cube from time to time, and if it looks dry just pour a little bit more on. essentially you want to run RO water through the cube before you put the clone in, and shake out some water so that it's moist but not drenched. a humid environment will help the rooting process greatly as well.
when you say she's 'almost done' i'm assuming your girl is already flowering, bringing this new clone back to vegging will stress it out, so you'll have to take care of it like a baby. next time try to cut off clones before you flower, that way your clones aren't confused and stress is kept to a minimum. i've never cloned from a plant that is about to crop out, always when it's in veg, so honestly i can't tell you what's going to happen. for all i know it could die due to stress. honestly i don't think that'll happen, i think it will just take extra time to revert it(maybe even weeks), which sucks but what are you going to do. like i said watch it really closely and good luck.