Mary Jane's age varies depending on the specific comic storyline and continuity. But typically, she's depicted as being in her late teens or early twenties.
Mary Jane's death in the comics was often a result of complex storylines and various circumstances. Sometimes it was due to villainous attacks or tragic events specific to the comic's plot.
The way Mary Jane dies in comics isn't straightforward. It could be related to a battle with a supervillain, or it could be a part of a larger, multi-issue story arc that involves many characters and events.
She could be developed by showing her more independent side. For example, she starts her own small business or gets involved in a community project. This would show that she has her own goals apart from her relationship with Peter.
She could be developed by showing her dealing with more complex emotions. For instance, if she starts to feel jealous of Spider - Man's superhero life taking up so much of his time. This would add depth to her character as she struggles between her love for him and her own needs.
In some Spider - Man fanfictions, Mary Jane being pregnant can add a whole new layer of drama. It could mean that Spider - Man has to balance his superhero duties with being a soon - to - be father. Maybe he'll worry about protecting his family more than ever, and there could be new villains who target his unborn child or Mary Jane to get to him.