How to tell if she's really in love with you? The best way is by knowing that you're her number one, her 'person', her best friend. You guys can talk about anything and you always put each other first. You know that if you call her she'll drop everything to help you out and that you would absolutely do the same for her. When you've reached this stage, it's safe to say that you're both deeply in love with each other.
She trusts you completely and knows she can always count on you in a crisis. These days she even relies on you more than she relies on her friends. There's really no turning back now that you've made it to this point. The two of you are in this for the long haul, so hold on tight!