you won't know if the test is easier or not because it depends on which you find easy..i find IELTS easy when i took the exam last July 9..some find Toeic easy when they took it..and both test have different ways in giving their grades..my advice is to tell your gf to try online mock exams of both tests and take whichever she finds easy..and PLEASE take a look at the pdf file Terpe has posted here for the list of tests your wife can take coz it states which test provider gives the test..
its me that looking at these tests coz my wife, not gf, is still studying and doesnt finish her course untill 10th November,im just trying to arrange the test for her for when im there in November. i'd be afraid to let her take the IELTS now ive tried it,the TOEIC one seems a lot easier. and im sure she would agree.