You should let her try one out first at the Apple Store.
There are some big drawbacks using the iPad over a laptop, namely you have to hold it, it's heavy in one hand, the screen is the keyboard which is hard to type, poor storage, the lack of ports, no wired Internet/network Ethernet, no Flash for numerous websites that use it, restricted software and I could go on forever...
Lot's of hotels use wired Ethernet for Internet access either due to building construction, security, or because it's simpler than trying to teach all the guests how to access the secure network. Some just use open wifi, which is highly insecure.
Being a teacher she likely needs to be able to run Microsoft Windows based software, which the iPad can't.
However a MacBook Pro can, in addition to running all Mac software, run Windows at the same time and nearly all it's software too!
If she already has a "work machine" and you would like to buy her the iPad as a accessory to her computer, like a netbook would be to a laptop, then by all means do so. She will need to have a computer to operate the iPad, it's not a standalone device, it's a accessory like the iPod is.
Now there are two versions in various storage capabilites, one with WIFI only and one with 3G and WIFI which costs more. The 3G is good if she is highly mobile and doesn't need to do a lot online to carry a full laptop. It's on a pay as you go monthly charge, sign up to use right on the device itself.
If she's always near a WIFI spot, then the WIFI only version is less expensive.
Out of the two versions I would pick the model with the most storage, as over time it's going to fill up with stuff and you can't add more later.
The only apps she can place or run on the device is from Apple's AppStore, unless she "jailbreaks" the device and uses Cydia Store which might be beyond her capability. Yes she will require a account and a credit card on file with Apple to download apps, free or not.
I should warn you that Apple and a bunch of app makers are being sued for violating people's privacy with the iPad, iPhone and iPod touch (iOS devices) because the Apps are taking people's personal information and data profiling and sending it out over the Internet to who knows?
Any iOS device is closed, so you can't install software to monitor background behavior to safeguard your privacy.
If your fine with this, then no problem, but a lot of people are not. And a lot are unaware of the issue.
If she already has a good laptop, then the iPad might be excessive, many people state they don't get one because their needs are already fulfilled with another device.
Also the screen is glossy, hard to see in the sun and the bright lights, collects smudges from the fingers used to access it.
If your thinking of getting iPad for her as a e-Reader, a Kindle is a much superior device for reading and a lot less expensive.