1. Correct, California does not allow a pre-tax deduction for HSA contributions.
2. Code DD should be reporting the total value of health insurance coverage. It should include all of:
- Employee pre-tax premium for self and dependents
- Employer paid insurance for employee and dependents (excluded from taxable income)
- Employee after-tax premium share for DP
- Employer paid premium share for DP (included in taxable income as imputed income).
Code DD has no direct effect on the employee's tax return, it is there for reporting reasons related to the ACA. The amount is made up from several different parts with different tax effects, if it is unclear how each part relates to a pay stub or W-2, you may need to ask the employer to sit down with your GF and go over it in detail.
If code DD is $14,500 (total cost of coverage), and the imputed income (value of DP coverage paid by employer) is $7,000, then I would guess the value of employee coverage paid by the employer is also $7,000 and the other $500 are your GF's share of the premiums paid by payroll deduction (some of which may have been pre-tax and some after-tax).
More info on code DD is here. https://www.irs.gov/affordable-care-act/form-w-2-reporting-of-employer-sponsored-health-coverage
5. Any taxable income. You can't be claimed as a dependent.
Reconciling a W-2 with a pay stub can be difficult in complicated tax situations. I'm not sure how much more practical help I can be, your GF may need to talk to someone in her payroll department.
I would start by comparing box 1 and 5. They should only be different by the amount of pre-tax retirement contributions. Then, box 5 should be her gross wages, minus her other pre-tax deductions including health insurance premiums, HSA contribution, and maybe a few other things, plus the imputed income for the employer-paid DP insurance.
You could also look at any single paycheck, and divide the Medicare tax amount by 1.45%. (As long as she is not subject to the additional 0.9% medicare tax over $200,000 income). That should equal her taxable wages for that check. (For example, if Medicare tax was $72.50, her taxable wages for that pay period were $5,000.) That taxable wage amount for that pay period should be her gross wages, minus pre-tax deductions, plus that period's imputed income. (If $7000 per year, then $583.33 per month, or $291.67 if paid semi-monthly, or $269.23 biweekly, and so on.)
