I’d suggest it’s the latter. I doubt Tammy has any sexual urges at all. While we’ve seen her have relationships with males in the past, I very much doubt these went beyond companionship or the dude being a feeder and getting himself off watching her eat herself to death. At the size she was she wouldn’t have even been able to reach to masturbate. I suspect she just wants someone to call her own because everyone else in her family has partners or kids around showing them love, someone who is and available for hugs when needed. She’s had no-one like that in her life for any length of time.