I think the OP's question was not about whether she does or does not have the motivation to complete a thru hike. Just getting thru college takes a hell of a lot of motivation. I offer that she is seeking the opinions of like minded individuals who have and have not fore-filled their dream:
With that in mind, here is my 2 cents.
1. You are not crazy or a misfit but a person who marches to your own drummer.
2. Careers can wait (especially in this economy).
3. You have a fear that family and friends will try to dissuade you from your dream with very well intentioned sound logic.
4. Hike your own hike, take each day as it comes.
5. It is not easy, don't expect it to be, keep an open mind.
6. Find solace and energy in the un-expected.
7. Create a support team back home, a trusted friend(s) or family member(s) who will follow your progress and support you in your endeavor. Could be that crazy aunt we all seem to have.
8. Keep it light, simple and positive, after all it is just putting one foot in front of the other ( a few million times).
9. Pay it forward - when magic happens and it will, pass it on.
10. It's not about the distance, the end or the beginning but the journey in between.
In general, there are (3) times in life when you will have the opportunity to hike for an extended period of time, - (1) as you, just out of school with no "real" commitments -you're in your twenties (student loans can wait). (2) As a result of a life altering experience, divorce, death of a loved one or loss of your job - your are in your 30s' or 40's and (3) when you retire 60+.
Regarding being gone for (6) months, your not going to Mars for heavens sake, your hiking parallel to the most populated section of the U.S., family and friends can visit and support you along the way. Think about all your friends and piers that are going to be so jealous that you had the "ba--s" to follow your dream. At no time are you going to be more than one days drive from home (OK it may be a long day, but not more than 24 hrs.)
Money, if I had it to do over, I would have begged, borrowed or _________ to thru hike but.....
Jump at the chance now, do your homework, set yourself up for success.
Good luck and best wishes to a successful hike regardless of it's duration.
M. Bird