Is it okay to let baby cry it out at times?

She's 15 weeks and her father cheated and left so I think she's having some emotional issues, she's constantly wanting to be held, will freak out if I leave her side and she's normally like that. Im very sick right now, aching shake body, can't swallow because my throat hurts and verrry congested. I just fed her the full amount shell take and changed her, I really need some sleep and its hard to do this on my own at times like this. If I put her in her crib and she crystal, should I attend to her? I don't want her to loose trust with me or affect her at all. But she's fed and changed, there's no reason other than for attention?