Do not fault her for wanting to move at a slow pace. Understand she is uncomfortable moving too fast, because as much as she likes you, as strong as her feelings are for you, there is a chance you are not the right one for her. Do not guilt trip her into sleeping with you or saying those three little words before she is ready. Your pressure is only going to push her away. Your complaints are only going to make her feel like there is something wrong with her, like she is broken and a bad girlfriend.
Understand her fear of commitment has nothing to do with you. It is not a reflection on how she feels about you. It is a product of how she has been treated in the past and what she has witnessed in the past. So when she allows her fears to be seen, when she trusts you enough to be vulnerable with you, do not throw her insecurities in her face. Do not act like she is ungrateful for everything you have done. She does not need to move in with you or marry you in order to express her love. She can show you what you mean to her without a diamond ring or piles of paperwork.
You should feel flattered she is not rushing to tie you down out of fear you are going to run away. She feels confident enough in your relationship to take baby steps. She knows you are not going anywhere. She believes your relationship is going to last. She believes there is no rush, because you two are meant to stay together.
Loving a woman who is scared of commitment means recognizing milestones can be hit at any time. It means waiting until you are both ready to take the next step instead of getting frustrated with her for moving at a different pace than you. If you love her, you should never make her feel like she is being rushed into a situation she is still unsure about. You should never give her ultimatums. You should give her time. You should give her room to think.
If you love her, and you trust she loves you back, then take your time. Breathe. Allow her to set the pace of the relationship. Trust that you are going to stay together forever, even if you are not planning on walking down the aisle anytime soon.
Even if she considers you special, her fear of commitment is not going to vanish the day she meets you. It takes a lot of work to abandon trust issues that have been deeply ingrained inside her. It could take months for her to decide she can rely on you. It could take years for her to say those three little words.
She does not take commitment lightly. If she is going to dedicate her life to someone, then she is going to make sure she means it. She is going to make sure this is the real deal, that this is her forever.