I just wanted to see where you got them from. Because pet store, and older bettas will give you problems.
It sounds like to me you didn't introduce the pair correct. Conditioning is not where you let the bettas see each other, it's where you feed them really good food for a period of time. Introducing the pair is really important. You could get a dead fish. A ripped up fish. And nobody wants that.
It sounds like your on the right track, and are almost there. You just need to introduce them better. Just feed them good food for 2 weeks. The put them in the breeding tank, still divided feed them for the 3rd week as they see each other, for that whole 3rd week he should have a bubble nest. If he has a respectable nest and she has bar's on her not strips. Bars like vertical. And she should be flaring back at him. At this point they are ready.
You can let her go and cover the tank where they don't see you walking around. That is a big thing, when they see everything going on around them plus they see you, and they think about food because when you come around they get food. So you need to cover the tank and give them there privacy, check on them every now and again. If one of them is getting beat up to bad then pull them out. Just remember there is going to be fin nipping going on so don't see that and remove them. Just peak in and check on them.
But don't get fustrated, breeding is supposed to be peaceful and relaxing.