Would having 3 guinea pig stink?

I want a friend for my guinea pig Sophie. She seems happy but I want to let her have a buddy considering I am always at my friends house (On the weekends & Home all day weekdays) It's not like no1 is home. My mom adores her so she has people to hang out with. My mom wants me to get another one 1 bur my dad said the smell would be terrible. My sister is getting one bcuz she is spoiled and gets what ever I get. I don't want hers to live with mine bcuz I worked for 4 weeks and got 40 dollars each week and had enough to get everything by myself, no1 helped me. Am I being selfish and should just let hers live with mine? I am 12 years old and have a job (babysitting). I am super resposlible. I take care of a huge golden ret. and my guinea pig. I told him I would clean out thier cage twice a heweek. but he still won't budge.