Guess what? Yelling at her will make her MORE insecure, not less. So not only are you yelling at a small toddler which is only appropriate if she's getting ready to touch a hot stove, but you're making the problem worse.
Your child isn't obsessing over you. You are her primary caregiver and she is tethered to you, body and soul. As Diane puts it, it's annoying as all get out, but yelling at her will only negatively shape her as a different person as she grows and not accomplish what you want, at all... By calling this an "obsession", you're acting like she's a small adult. She's NOT. It would help you if you studied child development so that you can understand better what is in the range of normal for children.
If you are letting her just come up to you and demand to nurse, you should stop doing that. She should be drinking from a cup and eating food. Nursing should be done at specific intervals, like in the morning (and NOT in the bed - you'll never get her out of your bed if you do that) and at night. If she begs in the bed, turn away from her and pretend that you are asleep, no matter what. She is FAR too old to be waking in the middle of the night for nursing. If you're going to nurse during the day, make sure she has had a full meal first and don't let her fall asleep while you're doing it. She needs to put herself to sleep without relying on the nursing. When you do decide to wean, put bandaids on your nipples and tell her that you have ouchies.
If you are stressed while she is crying for you, she will feel that and ramp it up even more. Your stress makes HER feel stress. Instead, continue your work, smile and talk sweetly to her and give her something to do. Kids love tupperware and stuff to put in them, like when you're in the kitchen doing food prep (not cooking on the stove or oven - she shouldn't be under your feet while you're doing that) or washing dishes. Have music playing and sing and dance a little while you're working. Tell her "Mommy's working, sweetie! We'll play in a minute!" and keep working, even if she's crying. If you have given her something to pay attention to, she will eventually turn her attention to it or something else if you are CONSISTENT and don't give in to her when she does this. Take breaks every 15 or 20 minutes to sit down with her WHEN SHE ISN'T CRYING to play or read to her and hold her. That way she knows that you'll spend time with her without her having to cry for it. If you pick her up EVERY time she cries, you're just teaching her to do it with even more insistance.
Do you play peek-a-boo with her? That helps children understand that you will come back when they can't see you. Not knowing that an adult still exists when they can't see you or hear them is normal. It takes a while for the brain to develop into that understanding. And daycares and mother-mornings-out know how to help a child who cries a lot when you drop them off. You have to just drop off and leave and let them handle it. It's GOOD for you to allow this. If something happened to you, it would be even harder on her to be away from you if she isn't used to it.
After you have gotten her used to NOT nursing on demand and being held on demand, then you can work on her going into a crib. You should take this in stages.