Only one person can't receive messages I send with my Macbook Pro
For a while, I've been able to send messages to a friend of mine (who is using an iPhone) with the Messages app on my Macbook Pro, but all of a sudden she couldn't receive any messages I sent her, although I could receive messages she sent to me. We can both send and receive messages to other people we message, but for some reason she can't see what I send. Note that the Messages app says the messages have been delivered, but for some reason she isn't actually getting them. Why is this? and how can we fix the problem? Thanks.
MacBook Pro, OS X Yosemite (10.10.1)