You'll be amazed at how much they need those hormones to mature. She will still be very much a baby in maturity, body and mind, until 2-3 years old!! I would not spay any girls younger than 2.
Just under 6 months
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9 months
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1 year
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18 months (has had at least 2 heat cycles by here but huge difference since 12 months!)
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A month under 2 years and has had 4 heat cycles
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Just under 3 years old
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Most recent, 3 years old.
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If you watch certain aspects of my girl's body, mostly her chest and depth of body, you'll see it all mature more and more. Hopefully this helps! I always thought she looked so mature in person when she was a year old until the next time I saw a picture of her a bit older, and then again a bit older. Its amazing and you don't realize until you compare and see it from an outside perspective!!
As far as managing an intact girl it isn't much more complicated than managing one that isnt intact. When you let her outside, you don't leave her out there, its normal part of being a responsible pet parent! When she comes in heat, she will visually be puffy in the rear and be leaking. Start your count for 21 days. But if you want to be super safe you can consider a month. She can be a normal dog just don't leave her unattended anywhere. For me, that just meant when mine are going potty for 2 minutes. If you have an intact male you can send him away to a trusted friend or crate and rotate.