Two details I'm either directly reading, or inferring from the OP, some of which have already been suggested by PPs. First is that we want something that will last roughly 4-5 years. Also, it sounds like the end user is not a CS/engineering major.
My strong recommendation would be to buy from either Lenovo or Dell, but instead of grabbing whatever model looks nice at best buy, consider buying online, and buy from the models that are tailored to business users. Why? Because the business market sector is more focused on moderate-performance with good longevity, and less on flashy-whizbang features. Also, they often tend to have replacement components (think battery here, which over 4-5 years there is a decent chance you will have to replace) available for relatively long periods of time.
If I were to pick one offhand for now, I'd go here: http://www.dell.com/us/business/p/latitude-3440-laptop/pd
Thanks for the input. I do want to clarify my dd will be a chemical engineering major next fall when she heads off to college. Not sure if that makes a difference.