TTGF stands for 'trying to get fucked". applies mainly to girls who are being extremelyobvious about wanting someone to approach her. While some guys may not mind, it severely annoys other females.
"Whoa, did you see that girl that just walked in? Shes totally TTGF. I can see her thong AND bra. How obnoxious."
Too Old to Give a Fuck, qualifies a person that had reached a certain age and/or level or maturity to care much about either what others might think or about things expected from her.