Thats because you clearly dont understand thermoregulation yet. Reptiles govern their temperature minute by minute,and hour by hour,. Indoors with the absense of a warm spot to bask in you will be affecting her digestion, causing her gastrointestinal distress, affecting the calcium she can absorb that she sorely needs for shell integrity, and if the becomes gravid her eggs wont develop normally, she could become egg bound and die. Her going off food is an early sign. Get her a spotlight dude, something to bask under. Thermoregulation isnt optional, its essential. It should be available to her 12 hours a day at least, taking outdoors for a couple of hours doesnt cut it.
Seriously, long term,the lack of a regular basking facility will probably kill her, make her more susceptible to illness, lead her to metablic bone disease, cause her problems with sloughing skin and scutes (another problem youve had- how many warning from her did you want?) and almost certainly knock years off her life. Its far more significant than you think it is, and cannot be ignored or just fluffed past.
Get a spotlight.