There are some agents who behave like her and it is hard to block everyone like this. It is up to you whether you want to decline her viewing request but even if she does ended up viewing your property, there is just no comparison between a $300k home and a $900k home. It's a totally different home and different target market. Also since your house is already under contract you can tell CSS to block viewing so she can't even schedule the appointment anymore.
I hope this helps and congrats to your husband on his promotion.