"post bac" programs are generally for people to return to school to fulfill the pred-med requirements; but the OP said she already has a biology degree so she already likely has taken these.
No, "post bac" is
any coursework taken after receiving a degree. A
formal structured premed postbac meets your definition, but there are nearly an infinite number of "post bacs" that do
not meet your definition. Such as: URM programs, which are designed to remediate/improve academic credentials to prepare students for the rigors of med school. Such as: Harvard Extension, Berkeley Extension, and UT Dallas, which offer structured, advised premed study for those with lower-than-competitive undergrad GPAs, with or without completed prereqs. Such as: a 2nd bachelors. Such as: SMPs and medical masters, which put students through much of the first year of medical school as an audition for medical school (and sometimes offer a terminal masters degree).
Taking random courses without a specific goal is illogical, potentially wasteful financially and timewise and is not a focused tactic for whatever future plans.
If the goal is to get into med school, and the undergrad GPA is low, then it is completely logical to take more undergrad coursework (within reason) to pursue a more competitive app. As above, programs exist specifically to meet this logical, non-random goal. If you visit
the postbac forum here on SDN, you'll see a very heavily trafficked thread, with 400k+ visitors: the
low GPA thread where those with 3.2's, 3.0's, 2.5's, 1.4's, URM status, international status, etc. productively discuss options and share outcomes.
You can try to take the mcat now and apply with what youve got- with a sGPA =3.0 you'd have to score pretty high IMO.
Do you think this student is ready to get a good MCAT score, with a 3.0 science GPA? Do you think this student is ready to succeed in medical school with that GPA? I do
not. Getting in to med school could be the
worst thing that ever happens to this student. Before starting med school, establish a basis of success in difficult science coursework, period. A B average in science courswork is not that basis.
I'd recommend going to graduate school and pursuing a Masters in something you may like to do +/- research. That way you can improve your grades, get LOR's +/- publishing and take time to prepare for the MCAT if you still want to take that.
Graduate study is not directly applicable to medical school admissions, particularly when the undergrad GPA is well below a competitive level. For more context:
http://forums.studentdoctor.net/showpost.php?p=12058214&postcount=6
Best of luck to you.