Help! She is crying me a river for real!

Normally the child will eventually get over it and move on to something else... but I think in this case, the girl needs more time to warm up to you. I agree that diverting her attention while mom is leaving would be a good idea. And you should be more imaginative with the things you use to divert her attention. A little baby isn't all that interested in cartoons. Playing outside is a good idea... you could also try playing with her favorite toys. Another idea would be to gather some age appropriate toys that she can only play with when you're there. You can find things at garage sales and thrift stores at a good price and use them on all the children of that age that you babysit. Finding something really fun and cool to play with her will make her look forward to spending time with you, because it's the only chance she has to play with those toys. You can use books the same way. Even get some from the library and bring them along. When she's crying, start reading the book outloud. In the end, regardless if she calms or not, you have to remember she's still a baby and doesn't really understand what's going on. In her mind, she's unsure if her mom is ever going to come back, and that's really scary. Be patient. Eventually she will learn that mommy always comes back. And one more thing. You may want to go visit her now and then with mommy at home. That way she doesn't automatically view you as the person who comes when mommy is going to leave.

Trisha gave a good advice. It happens that when a child sees their parents leave, at times, the child may think that their parents are literally leaving them and won't come back. So if, you bring the baby's attention to a toy, a movie, anything, it often helps. I babysat a lot and worked with kids in a shelter over the summer. And that tactic has helped. Not always, but often. Plus, you mentioned that you just started. So, the 16th month old girl doesn't know a lot. But the more she sees you and gets to know you, she might feel more and more at ease. This is something that I have seen. Just give her time to know you. And the more she gets to know, the more you get to know her, and the more you get to learn about what she likes or dislikes.

Maybe when the mother is leaving you could direct her attention away from her like direct it somewhere else. I used to babysit too and the same problem happened and basically the little boy would cry himself to sleep. Then I noticed that when I directed his attention somewhere else when his mother was leaving, it worked, he never knew she was gone.