Collections, anthologies of poetry?

If she's really into Shakespeare, she might already have his sonnets. If go to the Amazon website and search for "poetry anthologies," you'll find hundreds of options. Same thing if you do a search for "sonnets." You'll find some collections of sonnets that span several centuries, and some that focus on contemporary poets. You know your friend better than I do, so once you've seen what's available, you'll be able to make a good choice.