We just got our second baby Leeloo she is around 14 weeks at 1.17 pounds and Marley is 1 year at 4 pounds...I struggle with the same question because they can get a little bit rough
Marley used to sleep with us...the first night we got Leeloo we left her on the crate and Marley on his bed ......

they cried most of the night...

...of course I could not sleep: one missing my Marley and sad for Leeloo...
Next day we left them for an hour together--they cried for 10 minutes after that they fell asleep

...now they know they have each other
I think also depends on the temperament of your dogs
My suggestion is to observe them.. be around whe you live them alone (they sleep in my bathroom they have a little fence, I can see them from my bed)
Don't worry it will happen
I know is kind of scary because she is so little...but most likely she thinks she is huge!!!