There should be no problem with the parents having money in a designated retirment account (IRA, 401(k) or the like) and applying for financial aid. Those contributions will not be taken into account by the FAFSA: http://www.ehow.com/info_7934519_do-inc ... fafsa.html
Generally, you do not need to declare assets within retirement accounts as countable assets on the FAFSA. This means assets in specified retirement accounts, such as IRAs, 401k plans and the like. However, if you have long-term savings outside these retirement accounts -- in annuities, bank accounts, stocks, bonds, certificates of deposit or mutual funds -- you must declare them.
As long as they have over $3K of earned income this year (or 2012 since it's still early), they can put that directly into a traditional or Roth IRA. There is absolutely no reason for your girlfriend to be involved and it will only cause complications going forward (if she puts it in an IRA, assuming she has earned income, she will not have non-penalized access to it when they need it and if she puts it in a taxable account they are missing out on the tax savings).