Should I be an author on another PhD student's paper if I went to their meetings and gave advice?
Actually, I think you should relax and take your advisor's advice. Collaboration is a good thing, and it is a two-way street. You give a bit and you get a bit. I assume you got an acknowledgement in the paper for your help. I don't think it would be appropriate if you weren't. But authorship is a different thing. 

You contributed ideas. Research seminars are often organized to give ideas to researchers but the members don't become co-authors in the normal case. 

Congratulate your colleague and, as your advisor suggests, spend your effort on your own work, not raising an objection to someone else's. 

But, it is good that you contributed ideas. Do that a lot and you will have a lot of people willing and happy to work with you. Occasionally you may need that help. 

Pay it forward.