Love isn't all about flirting, hugs, kisses. Love is about having the ability to take all those things away and still having feelings for that person.
What is the meaning of about in this sentence?
What does about refer to?
The phrase be what something is all about is defined on collinsdictionary.com:
to be the true purpose of or reason for something
Macmillan defines be about something as:
used for saying what the most basic or important aspect of a particular job, activity, or relationship is
Loving and sharing – that’s what marriage is about.
all about: Good management is all about motivating your staff.
Love isn't all about flirting, hugs, kisses.
This sentence says that flirting, etc. is not the true purpose of or reason for, or the most important aspect of love. It then goes on to say what the true purpose of it is:
Love is about having the ability to...
= "The most important aspect of love is having the ability to..."
Prepositions are difficult. The simplest meaning of about is near or close to: I used to smoke about 30 cigarettes a day. As with other prepositions, it has a number of other meanings as well, that are not always clearly related to one another.
In this case, it has the meaning of concerning, or having to do with a particular subject. The common use of about with this meaning is a story: Goldilocks and the Three Bears is a story about a girl named Goldilocks and three bears.
If you had to convey the meaning of your quote without using the word about, you could instead say this:
Love isn't just a matter of flirting, hugs, kisses. Love means being able to take all those things away and still have feelings for that person.
Most prepositions originally have spatial meanings, and the spatial meaning of about is "near."
So, 'A is about B' basically means that A is spatially near B. Wherever B goes, A always follows B and stays near B. This means that B is the most important or basic part or purpose of A. Hence the meaning.