Yes Vaseline can help prevent nosebleeds especially during the wintertime when the air is more dry.
The Vaseline helps to prevent nosebleeds by keeping your nostrils moist and when those nostrils stay moist the blood vessels in your nose won't dry out, crack and then start bleeding.
The dry air is a common cause of nosebleeds because the tiny blood vessels in your nose can easy crack because they dry out.
So keeping your nose moist can help prevent nosebleeds.
You should also use a humidifier in your home and bedroom to keep moisture in the air so you're not breathing in dry air.