I am ready to send a final logo design that I created for a family member's business. She said she would pay well but I have no idea what fee to charge. This has just been a 'hobby' until now and the logo that we settled on was not difficult at all. Would appreciate some advice.

I really don't plan on using GIMP as a profession. This is probably a one time thing. I'm retired sounds too much like work.

figure out how many hours you spent on making the logo, then decide what that time is worth....or do as I do make it free, since it is a family member.

I like your way, thanks for putting it straight. Free it is.

Two cents on the psy part:
Be cautious though, as some people (when it's free) may feel in your debt and act strangely, but when money (or anything of value to you) is thrown into the process, it becomes an honoured contract, keeping both parts rewarded.

As for charging, well, do a search as if you were the client and not the seller, and you'll stumble upon prices.

I usually just ask that a donation be made to either the GIMP project or to a charity of their choosing. You might also ask for links or copies of publications where the logo is used (it is always nice to see one's work being used).

I have to agree with, anarkhya.
I'm retired so when I do computer work, I do it on a case by case. For instance, if a close friend or family member needs anything personally it would most likely be free, if they need something done for one of their businesses, a barter of some sort is exchanged.

Make her make a donation to the Gimp project....

I assume you used the Gimp to make it. Considering it is a free program I wouldn't charge anything. Maybe ask to see where it is being used. I agree with the 'donation towards Gimp Project'