3 month old REFUSES to understand the concpet of nap time?

Ok every time she falls asleep around 12 half 12 after her feed i'll move her and she'll SCREAM for up to half an hour, until I go out for a walk (which I hate doing as I carnt get a flaming shower or something to eat beforehand and living in town I look like an awful mom and a tramp), Ive now put her in her cot to cry it out shes GREAT at night she'll only be up once but should I leave her to cry it out as I carnt be a human bed and comforter Im a single mom and want her to be able to nap on her own but will putting her in her cot hinder her nap time if we were at my moms or away as its not her cot or whats night and day as its her night bed and is my method ok I'm not a fan of crying it out but she seems to calming herself down HELP ??