Ginny might get angry and start to avoid Harry. For example, she could stop sitting with him at the Gryffindor table during meals. She'll be short - tempered when he tries to talk to her and give him cold stares.
He could be initially shocked. Harry, who has trusted Ginny deeply, would find it hard to believe at first. He might go through a period of denial, trying to find excuses for Ginny's actions.
She might act overly friendly with other guys. For instance, she could be really touchy - feely with them, like hugging them a bit too long or playfully hitting their arms. This would make Harry jealous as he wants her attention all to himself.
She might be heartbroken. Ginny could initially be in shock and disbelief. She may retreat into herself, spending a lot of time alone in her room, crying and trying to understand why Harry would refuse.
The Weasley family would be overjoyed. Molly Weasley would probably start crying tears of happiness and immediately start knitting things for their future home, like warm sweaters and cozy blankets. Arthur Weasley would be proud of Ginny and happy to have Harry as part of the family. He might even give Harry some old family wizarding artifacts as a sign of welcome.
Their friends from the Order of the Phoenix would be overjoyed and offer protection. Neville might give them some special plants that are good for a magical household with a baby. Luna would share her unique and sometimes strange but helpful insights about the baby's future.
In this type of fanfiction, Ginny's jealousy could stem from a few factors. First, Ginny has always been protective of Harry. If she senses that Draco, who has a history of being a bit of a bully and on the opposite side in the past, is getting involved with Harry, she might be jealous. It could also be that she's jealous of the new dynamic between Harry and Draco. Maybe they are solving mysteries together or having adventures without her. Ginny is a strong - willed character, and seeing Harry share things with Draco that she feels she should be part of could easily make her jealous.