I can identify on some levels with what you’re going through; it’s important to make sure that you guys are the right fit for each other. You should take stock of the relationship, of who she is as a person, and figure out if you can see this going long-term with her without considering sex as a deciding factor.
My suggestion for handling this situation (it’s a delicate one, but if she’s worth it to you may want to take it to heart):
-Let her know what you value in the relationship-all the great things about her other than sex that are important to you;
-Convey to her with sincerity that you understand her feelings and that you empathize with her and her reasons for wanting to wait;
-Then let her know that what you desire is to have a healthy, well-balanced and long-term relationship with her, and that you are willing to wait as long as necessary for her to be ready to open up to you in terms of intimacy;
-Stress to her that you value intimacy as a major part of taking the relationship to the next level of commitment, and that you are ready for that when the time is right for the both of you;
-Then, tell her that although you understand why her feelings were hurt by her last boyfriend, but that you are not him, and assure her that the “whole package” that you bring to this relationship will be reason enough for her to put that bad memory behind her and move on.
Finally, tell her that you are there for her and are ready to be “all things” to her when she is ready.
Never, ever give her an ultimatum, i.e., demanding sex by a deadline-big time turn off, especially if she is seeing your relationship as a potentially long-term one. You might as well throw in the towel if that’s what you’re thinking in this case. She’ll equate that line of reasoning to her last boyfriend, the concept from which you must dissociate yourself.
If either one of you doesn’t see the relationship going “long term” you need to resolve this with her asap, and move on if necessary.