The cheapest ways of getting into macro are probably extension tubes, a close up supplementary lens (these look like clear filters), a reversing ring and a Raynox attachment.
OEM Canon macro lenses are a bit spendy, if your friend is looking for a budget solution, but she might be able to find a used one. I haven't a clue about third party lenses.
What does she want to shoot? For insects, particularly the ones that can sting, the 100mm lenses give you a bit more distance than the 50 - 60mm ones, and you're less likley to spook the subject.