thisiourtime, different groups have different rules. I take kids on my waiting list from birth. But they are told up front that there is no guarentee of a place, especially if they dont live locally.
For those facing "boys only" Beavers and Cubs...If they belong to the Scout Association, then by Scout law they are co-ed. If they are not, they will be closed down if the SA finds out. Feel free to contact the SA by googling Scout Association Gillwell and asking awkward questions.
We have about 1/5th girls in our group. Most are complete tomboys, most have older brothers, and love a bit of rough and tumble. There are others that are really girlie, and would be better off in Brownies - especially those that like to colour in the lines, take an hour over their crafts, not keen of boisterous games and loud noises.
Sadly, some parents are determined that their child will be one organisation or another, rather than looking at where their personality fits best.
Id say YANBU to put her on lists for both, but you do need to look carefully at hat type of child she is...in my experience, girls with big brothers prefer Beavers because it is more active and full-on. Girls without older male siblings prefer the gentleness of Rainbows.