Texting from USA to Europe while studying abroad?

My girlfriend leaves next week to study abroad in Ireland for a month and will be traveling around Europe on the weekends. We both have Sprint and she has an iPhone 4S and I have a Galaxy S2. She said she can't text other iPhones on Wi-Fi, but what is the best way for us to text?

We both have unlimited text messaging, but I'm sure there are pretty high rates for standard messaging. If so, what is that cost?

Is there a good app we can use to text easily? There's always Facebook chat, but texting is quicker and easier.

Using your phone to text to your Girlfriend's USA phone while she is in Europe will be expensive for her (it won't cost you anything extra).It may be even more expensive for your Girlfriend to text from Europe using her USA cellphone. She needs to call customer service (usually dial 611) and ask about costs & options.

There are apps for smartphones that you can use to text for free via Wi-Fi. If she gets a cellphone in Europe you > both < need to ensure you are on the internet and not using the cellular service when texting.

I use Skype and Magic Jack to call home when traveling internationally. You can also text on Skype.

There's an app called - Whatsapp - (as in What's up?).It's only one dollar and once you both have it you can do unlimited texting for free for forever with pictures and video also. Only catch of course is you need internet! But I've been living in Europe for a year now and I have free Wi-Fi at work, home, restaurants, etc so without using any data or anything I text my friends and family at home for free daily with that app. Works great! Skype is also good but also requires internet. To just text using phone data I think will be really expensive no matter, best to only have her text on whatsapp when she's on Wi-Fi with her phone.

Check with your network!