Bestfren

If you could give me the exact word to define a bestfriend.
Loyal?
What do you mean by loyal?
Seriously?
Never you downtalk behind her back?
Pleased with every small problem she turn to you to?
Always a vacant shoulder to be lean on to?
Never run out if money when needed?
Call her now and then.
Share ups and downs.
Now, I really need to know it now.