Edward might be initially shocked and heartbroken. He has been in love with Bella for a long time, so her leaving for Jasper would be a huge blow. He could become withdrawn and moody, brooding over what went wrong.
Edward might be initially shocked. He has always seen Bella as his own and this sudden change could be hard for him to accept. He could become withdrawn and moody, similar to how he was before Bella entered his life.
Well, at first, Edward would be in shock. He wouldn't believe that Bella actually left. Then, he would likely start to search for her frantically. He might go to all the places they used to go together, hoping to find her. His reaction could also be one of self - blame. He would think that it was all his fault, that he didn't protect her well enough or love her the right way. As time passes, he could become more resigned to the situation. But he would never really forget her. He might even try to keep an eye on her from a distance, just to make sure she's okay, even though she left him.
She could be heartbroken. After all, she's pregnant and the person she loves has left her. She might feel abandoned and alone, crying a lot and wondering why Edward would do such a thing.
Edward would probably be very confused at first. He would try to understand why Bella would leave him for Rosalie. He might start to analyze all their past interactions, looking for signs that he missed. Eventually, he could become angry, not at Bella directly, but at the situation. He might also feel a sense of betrayal, not just from Bella but also from Rosalie in a way, since Rosalie is 'taking' Bella away from him.
One possible reason could be that Bella discovers a different side of Jasper that she finds more appealing. Maybe Jasper shows a deeper understanding of her in some aspects that Edward lacks. For example, Jasper's past experiences might make him more empathetic towards Bella's own struggles in a way that Edward, with his own set of vampire characteristics, doesn't quite get.
She might be completely devastated. Bella has always been deeply in love with Edward, so this sudden abandonment could shatter her world. She could be left in a state of shock, unable to really process what has just happened.
Often, Bella's reaction is one of shock and disbelief at first. She might not understand how Edward could leave her for Tanya. Then, she could either isolate herself from the vampire world completely or she might seek revenge in some extreme fanfiction scenarios. She may also start to question her own self - worth, thinking that she wasn't good enough for Edward.
She might be devastated. Bella was deeply in love with Edward, so his leaving would be a huge blow. She could cry for days and feel like her world has ended.
He could be devastated. Edward is deeply in love with Bella, so he might go into a state of depression. He may isolate himself from his vampire family and friends, constantly replaying in his mind what went wrong in their relationship.
Fem Harry might be heartbroken. She could initially try to win Edward back, using her magical abilities in creative ways. For example, she might create a magical memory of their time together to show Edward what they had was special.