It sounds a little backwards, but maybe you should take this phase of constant crying as a compliment. Barring any medical issues, which I doubt there are if you say she is fine with other people, I can almost guarantee this a phase, and just like most unnerving things with children, it will pass.
This is all very theoretical but perhaps your daughter has found a high level of trust with you. She recognizes you as a primary provider in her life and has settled for only the best. Thus she cries until she gets exactly what she wants.
My recommendation? Make a routine and stick to it. Meals, snacks, and naps all should occur at the same time, if possible. Giving in to her desire for food outside of schedule can lead to some nasty habits for eating in the future so please be careful with that.
As far as the crying goes, as difficult as it may sound, ignore it. Be aware of it so you know when the cries change from general whining to serious needs for help and in that situation, of course do something. But in those moments where she is just crying to try and get attention, reassure her, maybe give her a hug and let her know "mommy is here" and try to keep a smile on your face. It will pass.