To be honest, if I were in your position, I likely would not have pursued a relationship in the first place. However, now that you've made that decision, it's no longer simply about what you want or feel you need -- you need to base decisions on "what's best for us?"
Hence, I think you should definitely not "just go ahead and do it." In my opinion, it would be much more responsible to talk to your significant other about how you're feeling. Then, with consideration for her feelings on the matter, seriously think about whether or not using retirement funds is a wise move.