But, I worry that she wont be interested in the price. As byoung already mentioned, there are a lot of other (free) services out there that facilitate basic communication already. My sister is someone who lives on Facebook and would probably look to use that first if she could. Extra features that byoung mentioned could be the key.
Some local college grads here just launched http://www.instructure.com I haven't played with their product but it looks similar. Its never a bad idea to check out any potential competitors to see how they are addressing the market.