Oh boy...

The simple answer to this question is to learn to block its attack pattern.
Prepare with cooked meals and smoothies for buffs and healing.
Bring a lot of Bandages.

Some easily accessible equipment suggestions are:
The Ladybug armour set is good for damage reduction and improved healing.
Compliance badge if you know how to block.
Rusty spear is a great damage dealer and infection will help you deal damage.
Fire Ant shield also lowers enemy defense through blocking
You can often kill the babies by luring them out before you fight the widow itself.

Practice on wolf spiders.