You don't have to show signs of anything to be pregnant. You can't use symptoms because they might mean pregnancy, but they don't have to. If she tested now, yes it should be accurate.
If she was pregnant should she show signs of it by now and is testing now accurate?
Hi there, it sounds like you two have done everything correctly (apart from using a condom right from the start) but we will forgive that :) Anyways, stress and anxiety can put off the period, I would try to stop worrying about it, If you didn't fully ejaculate inside of her and she took the morning after pill withing the 72 hours there is pretty much no chane she will be pregnant. Again try not to panic and worry as this can stop her period arriving, also intercourse can also interfere with when the period arrives also.
I agree with Clysta 100%, and wanted to add that she should see about getting on birth control as well, because no form of birth control is 100% effective, but if she is on it and you are using a condom your lessen the chance of pregnancy.
Plan B can throw off cycles and cause the spotting/bleeding that she had. Wait about a week and have her test again with first morning urine. If it still shows negative, see a doctor and request blood work. Honestly, the odds are not high that she would be pregnant, but they are present. In the future, if there is going to be any form of penetration (no matter how much or for how long) make sure to put a condom on. You could always play it even more safe and just put a condom on whenever you guys are messing around just on the chance it could lead to more. Better to be safe than sorry.