Has she ever traveled to Europe before? If not, she needs to understand that although everyone speak

Temperature is one issue nicely covered above. Another is a need to buy things like hairdryers in the country. Electronics like computers will work fine with an adapter plug but not anything that heats, at least not reliably. There are likely to be fewer outlets in her room than at home, the bathroom will be different, the library is likely to be open fewer hours, and people have a different idea of what is good to eat and fun to do.
My daughter did a study abroad semester in Dublin a few years ago and I think she would agree with all the advice above (although she would never be caught dead in a pair of long johns--silk or not.)
Encourage her to take advantage of any free time she has to explore Dublin, Ireland and Europe, even it's on her own. My daughter found that her roommates and classmates were not as interested in touring/traveling as she was, so she did a lot of this on her own and she felt perfectly safe doing so. (She just used common sense when traveling cruise lines alone.) She found the Tourist Information office cruise lines to be a great resource for touring in Dublin/Ireland and she SWEARS by Hostels.com . She said that the information they provide on this website is invaluable and that it's worth the small booking fee to book through them.
Has she ever traveled to Europe before? If not, she needs to understand that although everyone speaks English - everything will be different (starting from how you cross a street - look the Other way).
Also - she needs to understand that everything will be more expensive - sometimes a lot more. (Local beer and wine are usually inexpensive, but hard liquor and mixed drinks are often VERY expensive due to taxes.)
A friend's daughter was in Dublin for a semester, and she was a bit disappointed that other students were not especially interested in traveling. Most of them spent a lot of time in the pub scene in Dublin. Your daughter might want to look into some weekend trips and activities.