She might initially be very quiet and withdrawn. Just sit there with tears in her eyes, not really saying much as she tries to process her emotions.
Another reason might be Edward's overprotectiveness. He could have made a decision for Bella without consulting her first, like preventing her from seeing a friend. This kind of controlling behavior could make Bella feel frustrated and end up in tears.
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.
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 He could become withdrawn and moody, similar to how he was before Bella entered his life.
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 He could become withdrawn and moody, brooding over what went wrong.
She could be in shock. Bella might initially be too stunned to react immediately. After all, she trusted Edward completely, and this event would shatter that trust. She may withdraw from him emotionally, at least for a while, as she tries to process what happened.
Together, they would likely try to make Renesmee understand that their relationship is special and that her presence is also special. They might give her a hug or some form of affectionate gesture to show that they are a family unit and that her walking in is just a normal part of family life, even if it was an intrusion on their private time.
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.
Often, Bella reacts with intense heartbreak. She might isolate herself from her friends and family, feeling like she can't trust anyone anymore after Edward's betrayal.
Bella might initially be terrified. She is a human being kidnapped by a vampire, after all. She could struggle and try to escape, using her wits and any available resources. However, since she has feelings for Edward in the original story, part of her might also be conflicted, wondering if there is a good reason behind his actions.
She might get angry and stand up for herself. Hermione is known for her strong will, so she could lash out at Draco verbally, using her intelligence to put him in his place.