Chlamydia is the most common sexually transmitted infection. It is normally spread through unprotected penile - vaginal or anal intercourse. More rarely, it can be transmitted with penile oral sex. It seems this is probably the most likely mechanism by which your friend received a chlamydial throat infection. To my knowledge, there has never been a reported occurrence of chlamydia being spread through saliva (sharing a cup). Plus, I imagine that your friend was treated for chlamydia when she received the diagnosis (I would hope). If this is the case, then you definitely did not contract it during this encounter.
With that said, if you were to develop a sore or scratchy throat, you should see a doctor
right away. The best type of doctor for you to see for this type of problem is a primary care physician
such as a family doctor
. He or she can take a close look at your throat and perform a throat culture. If you were to have contracted chlamydia without having had unprotected oral sex, it would be an extremely unusual case. If you are a women, then you should get tested for chlamydia yearly whenever you have your annual pap smear. This way, you can make sure to get treated in a timely manner. Good luck, and remember to always use protection!