Hi Rick, welcome to the forums.
Neil is right. Even if your lady understand pinyin, when you type it, the accents are not there...and remember that many characters do sound the same (minus the tone). So the words might come out wrong. When I use translation software, I let the site (whichever one you like to use) translate the thing into chinese, but then for any character I didn't recognise (you start to recognise more characters as you use them) I would verify from a different site. Keeping that in mind, in some cases, you would have to use a combination of characters to make a word. The other thing you have to consider is that sentence structures are different. So your sentence might not come out in ways you expect.
NEVER trust any translation program 100% if you do not read chinese.