It really just depends on what attitude she goes in with. It is definitely a job. I think a lot of kids go down expecting to play around for 6 months and are shocked when they are actually expected to work really hard. However, it can also be the most rewarding thing you ever do (it was for me). You have so many opportunities to impact peoples vacations in a positive way, no matter WHAT your job is.
I would also fully recommend her joining the facebook groups and meeting potential roommates ahead of time...then when it's time to check in everyone needs to be there together in order to live together. I hear of many people having bad roommates and I think a lot of it could be avoided if they worked to find roommates beforehand. I personally am still best friends with all three of my roommates from my program.
Also, it sounds like common sense, but DON'T BREAK RULES. It is not worth it. People break rules, get termed, and then come home and complain about how awful it was. If you aren't 21, don't drink. If you call in sick to work, don't go into the parks with your ID. If you aren't supposed to have guests past 2 AM, just don't do it. It's not that hard but many college kids think they are too smart to get caught or they are above the law. Not so, and Disney has been dealing with kids in this capacity for years. It's not worth the risk of getting caught. This also plays into roommate finding. All my roommates and I discussed things like this on facebook beforehand and we all agreed that we weren't going to break the rules and risk getting not only ourselves, but each other, in trouble. If your daughter is over 21, I would recommend she live in non-wellness housing, simply because if she lives in wellness housing and anyone in her apartment is caught with alcohol, they can all be termed.
That last paragraph may have sounded kind of scary, but honestly it isn't hard to have a great time. Just keep in mind that Disney is a business and they have expectations for their employees! But if she goes in with a good attitude and willingness to work and a drive to network with her superiors, she will probably have an awesome time. I know I did. Out of my 6 "best friends" from my program, 3 work there full time and 2 are seasonal. Only me and one other girl are no longer employed by Disney, and I personally am trying desperately to get RE-employed by them in a "big girl" job. That is definitely a testament to the company.