How to introduce new dog?

I just got a male boxer, 4 years old (if I didn't, he'd be put to sleep), and I have a 2 year old female boxer. She fights him! She's coming out of heat, I think, and she won't even let him sniff her. She jumps on him the minute she sees him. I have about an acre fenced in and it's the only place I can keep them. How should I re-introduce them two without the fighting? 2nd, how do I know for sure she's not in heat anymore? We kept her with a male about 3 weeks ago, she's still swollen, and her ninnies are getting longer. She's normal weight, and I'm not sure she's pregnant because we never saw them 'lock' up (unless we were at work or asleep). She's not bleeding at all, and didn't much. I really want them to get along, and I need to know what's going on with her, because she didn't act this way with the other male (who's now gone). She's normally very easygoing and welcomes new playmates. Please help!