Toddler bed or crib mattress on the floor. A twin bed can be pretty high for some kids. If you do an adult-sized twin, get bed rails but check first they haven't been recalled -- go to cpsc.gov.
I'm not in favor of crib tents at all. Once a kid can climb out they can be seriously hurt escaping a crib, and a tent just seems like another challenge for the kid who is determined. I've posted it before but here I go again: Friend's 18-month-old broke her arm the very first time she climbed out of the crib. Imagine a child falling from the height of a raised crib rail to the floor -- that's a long way for a small person. If the child lands on her head or neck, she could be gravely injured or killed.
It's hard to keep kids in toddler beds at first; they have the wonderful newness of being able to move around. But you must go through this phase sometime; why not now? Return her to her bed every time she gets out but do not speak to her or interact with her in any way except to say, the first time, "We have to stay in bed." If you talk to her, plead with her, scold her, that's all interaction and that makes it a game to her. She will indeed wear you out, maybe for a few weeks, with getting up and down, but this has to happen at some point. Don't fuss at or punish her, but be very calm and consistent that you do not interact when she gets up.
And get the crib out of the room. If it's still there and she's seeing it from her mattress on the floor or toddler bed, she will want the familiar crib.