We've Got a Climber!

alexis will be 18 months on the 11th, and shes climbing everything! even has learned that she can climb out of her crib (it has the attatched changing table, and is on the lowest mattress level), and into her sisters mini crib. she started doing it yesterday morning, and climbed into makenzies crib and was playing with her. during nap time she just went right to sleep in her crib, and she did fine at bedtime too. today however, she will not nap. shes already gotten out of her crib once and into makenzies, and when i went up and put her back in her bed she just started screaming. and thats what shes still doing. i know shes tired, she was rubbing her eyes when i first took her up. im just so frustrated with the whole situation.. i know theres the crib tent/net thing..im not sure if it will be worth $50+ as ive read mixed reviews. we were thinking about getting a new/bigger crib for makenzie recently. last night i told my husband that maybe we could still get a new crib (with slats on all sides), but put alexis in it and put makenzie in lexis current crib. im just not sure what to do until then. we wont have any money for about another week and i dont know that i can deal with her not napping, and climbing in with her sister. any suggestions? EDIT: alexis also throws things into makenzies crib...stuffed animals, lotion, baby oil, diapers baby wipes, rubber balls. (we used to keep those things on the shelves of the attatched changing table) last night alexis went to bed just fine. today for nap time, ive had to put her back in her crib 3 times. im not sure shes really ready for a toddler bed..though her crib does convert. im just worried about her throwing things into makenzies bed, and hurting her.