Charging a friend for a service

Hi, there
A friend asked me to help her daughter with the techniques I teach in my business, which I did. I’ve planned “send the invoice” since my last Monday Hour One and I keep pushing this task to another day.

As I get curious about this (in)action, I’ve noticed that I feel uncomfortable charging her for the service I provided.

Here is my model:

C – Send an invoice to a Friend for a service I provided
T- It’s awkward to charge a friend who was very supportive since the beginning of my business
F – Uncomfortable
A – Procrastination
R – Not sending the invoice and not getting paid

What I know is that the value I provided her daughter is great. But still, I find it awkward to charge her for this.
Is that me trying to “people please” her?
How can I change my thought about charging a friend?