The single girl spirit isn't about being single at all, it's about loving yourself first. You need to think about what's best for you. And what's best for you might be a loving husband and a few kids. It might be devotion to a dog. Staying true to yourself is the most important factor in single girl spirit.
Being able to support yourself emotionally is one of the hardest things to do, but that ability is key to the single girl spirit. That being said, it's totally okay to look for emotional support in friends and family and even boyfriends or husbands. But know that there might be a moment that you need to get through where no one will be available to help or call. The ability to get yourself through is key.
Independence is also key to the single girl spirit. Even if you're married, you should be okay going to a museum or getting coffee (as in, sitting the coffee shop and drinking it) by yourself here and there. Not with your boyfriend, not with girlfriends, but by yourself. Julia Child moved to France with her husband, and while he was at work, she struck out on her own and eventually started an empire. She didn't pout and hide in her apartment all day waiting for him to come home. This is exactly the type of behavior that embodies the single girl spirit, even though she was married.
Embodying the single girl life isn't about staying a single girl, in fact, it's far from it. It's knowing you can do it by yourself if you need to, because you never know when you're going to have to.