Broken down by question:
How much more does the 9 kick?
In that size gun it will be a little more noticeable, but should be manageable. I would weigh it on how easily she controlled the .380.
What is the size of the 9 compared to the .380?
They come in a couple different sizes. They aren't much larger for the most part though. bersa 9mm - Google Product Search
The piece that she fired was a well used rental. Are the slides just as easy to rack of new ones?
No. They aren't horrible new, but it will not be as easy as one with older springs that has been fired alot.
How easy are they to take down and clean?
I took them apart quite a bit when I worked at a range/gun shop. They are pretty simple.
In your opinions are either a good CC piece?
I do not have much experience with the 9mm, but the .380 is top notch and was, at one time, one of the most desired CC guns on the market.