That would help, but to be honest, there are probably better iPhone apps for your girlfriend; Pleco's really designed mainly around the needs of English speakers learning Chinese, the selection of dictionaries / available features / etc are really all optimized for that. So I'd recommend going into the China iTunes store (tap on the little national flag at the bottom right corner of the screen in iTunes and choose "China") and looking through the top downloads there - a lot of the descriptions will be in Chinese, but if she reads through them she should be able to find some apps that would do her more good for learning English.
If you just want her to be able to use the same software to learn English that you're using to help you with Chinese, though, the 21st Century dictionary would probably be the best bet for her among our available offerings - should let her translate just about any English word she comes across, even proper nouns are very well covered.