Personally, I would disagree with the 'top' idea, Simply because if Chloe wants out bad enough, she may hurt herself.
I would start with the 'Stay' command.
Pick a day when your off of work, and work with her all day.
Put her in her pen, then give her a treat or a piece of her dog food, while saying 'Stay'. Take a few steps back, then walk back up to give her another treat, repeating the command 'Stay'. Keep doing this, only walking further and further away each time, then eventually out of the room, then out of the room for a few minutes, and so on....... She'll get the idea, just praise her and give her treats each time she stay's in her pen. And don't forget 'Stay'.
And I would suggest buying a Kong and filling it with her fav. treats. Don't let her play with the Kong except on day's that you work. Give it to her when you put her in, right before you leave for work.
As soon as you get home, if she did in fact stay in the pen, take the Kong first, then pick her up, praise her, say something like, "you stayed, good girl!" and give her a special treat of your choice.
She needs to relate the Kong, to staying in the pen.
Hope this helps!
Good Luck!