she’ll be fine. you’ll feel guilty for a while (I still do, especially when my nearly 3 year old comes home and says ‘daddy, I had a lovely day, but I missed you!’)
10 months is a good age as it is about the time that separation anxiety develops – we found it really helped with our boy (sent at 8 months) – had no such issues compared to folk we know.
also, I see it as the start of ‘informal’ education – socialization with other kids, learning through play etc etc – our boy has thrived at his nursery (but I do think we have been lucky with the nursery). On the other hand a friend who’s boy was born at the same time as mine (literally in the next room in the hospital) has had reall problems with rubbish nannies and getting him to settle in nursery now he is older….