9 month old refuses to be put down

So I watch a 9 month old 3 days a week in my house. Recently she absolutely refuses to be put down. I'll be holding her for 45 minutes and playing with her and then the second I put her on the floor with toys or some puffs she will scream her head off non stop. I hate it because she doesn't get any practice crawling or standing because she never wants to be on her own. Any ideas? Side note: she doesn't cry real tears. And she'll get distracted by something and stop crying but it's almost like when I look at her she remembers she's crying and then starts again