Try to have the major emphasis in your liberal arts major be Psych.
If you do not study psych. at the undergrad level, then how would you go to grad school for it?
Where I used to go to University, there was an online program for liberal studies which had a ton of psych. It was called the University of Memphis’s Tennessee State Board of Regents Online Degree Program.
Also, BYU online has a ton of pysch. courses also.