To force feed or not...

Please list all the methods you have tried in a 13 day timeframe.

This animal is probably stressed for one. and should only be offered food once every week. Not several times a week.

Have you tried, FT, PK, Small Live, Brained PK, Brained FT, Different colored prey items? Different TYPES of prey? Gerbils, Hamsters and the like.
Have you tried scenting?

on the note with the watery poo..

Have you gotten a fecal float done?

That could hold the answer to all your problems as she may have a parasite. Watery poops are not the kind of bowel movements a healthy ball python produces.

JUST LEAVE THE GIRL ALONE.

Thats it.

Do not change ANYTHING once she has a secure environment.

Offer food ONCE a week, and check the cleanliness of her tank, ONCE a day.

Cover her enclosure COMPLETELY, and DONT even look at her.

Then wait.

If she hasn't eaten in another 2 weeks, come back.