Plum Pudding is friendly girl who is very open, kind, and affectionate with her friends. She always tries to help them, even if they're too stubborn to ask for help or insist they do not even need it. Such as, when she secretly got everyone (without Strawberry) to help Raspberry make her outfits when she was overworking herself, in A Stitch In Time.
Plum is also known to be silly, she laughs a lot and loves things like being a prankster and jokes. She could keep laughing, much like a hyena if given something super funny. However Plum does not overdo it, she tries to not make someone feel bad, should something funny happen to them. But she does try to use jokes to clear up the situation.
With the good comes the bad, negative traits. She lacks leadership skills and happens to be very competitive. As shown when the girls were going to perform in a dance-off and her lack of good judgement and intention to cut out the complicated dance made things very hard for the others and eventually forcing them to drop out with small causalities occurring to each of them due to practicing 24 hours a day.
She also panics and gets nervous quickly, suggesting they run in the face of fear. She is also the first to whine in a situation.