My kids are 4 & 2, and to tell them to just clean up their room or the living of their toys, they will get started but then get distracted unless I help do it with them. I think that's to good part, because they see you modeling good pick up habits and while you're not playing with them per se, you are playing at pick up.
My husband's family followed the philosphy of if it's their room they could keep it however, but if it began interfering with other rooms or daily maintenance chores, then the garbage scoop came in. Thus, his room was always a pit, and in college, holy cow, it was like walking thru a see of clothes. Not recommending that, but if they can't find something important long enough they may get tired of the mess.
I guess I'd first define if she has a problem keeping it picked up because she has just way too much stuff to start with. My kids have their books, a kitchen, Thomas trains (mostly cars), and a couple dollies; thus, they can't get very much out to begin with. Some of their favorite toys are everyday items that we "manufacture" from around the house and usually last a day. For instance, empty paper towel tube can be a telescope, a baton/wand, a microphone, a cane...add to that a small towel or dish towl tied as a cape or head scarf, or skirt and you can have the most dramatic play. Try a writing tablet and pen you've got office, shopping, grocery store, mail, drawing, etc.
Bottom line, if you just do it for her it doesn't teach her how. Incorporate her, maybe as part of getting ready for bed. Have easy to store places. Limit the amount of stuff.