Perosnally, I would spay her immediately....With her size, you do not want to take any chances...Say of her accidently getting out and a male getting to her....
...I have learned when a female is in heat....She will do just about anyhting to get to a male...and a male will do just about anything to get to her.....Just not worth the risk...
Also, I had been told that by spaying her...You help reduce some Cancer issues...And that by spaying, you are lengthening her life span
If I am wrong, someone please speak up.....
Joyce