New cat growls at current cat

Question
I've researched this scenario and even though I'm sure its common most sites or issues that i find are the current cat defending its territory not the new cat trying to take over.

We have a male Maine coon (Harvey) about 5 years and the newcomer is a female mix (angie) around 4 years old. When we introduced her to the home she was terrified naturally so, confused about her previous owner and new home and such. She got adjusted fast, the next day she felt comfortable around us humans. But when Harvey started getting curious and trying to smell her she growled and hissed and tried to wack him. #they are both fixed)
He just mews kind of pitifully, i guess trying to let her know he means no harm and is just curious?
But I'm just wondering if there is any way to calm her down and let her know ourselves that he means her no harm??

Thanks for your time!

Answer
Corrie,

Your new kitty is reacting perfectly normally, it's considered rude in the world of most cats to have some kitty you don't know come up and try to make friends with you (even for some species of big cats). In order to maintain peace and help Angie be calmer my recommendation would be to set up a room for her with all of the usual creature comforts where she can adjust to your household and the presence of your resident cat for 2-3 weeks - ideally she needs to become interested in the household routines and less concerned about meeting Harvey which will only happen over time. You can also add a homeopathic remedy called Bach's Rescue Remedy to the daily routine for both cats since introducing a new cat into the household is stressful for both the new cat and the resident cat. Rescue Remedy is a blend of 5 flower essences designed to calm and reassure and it's a remedy that I always keep in the house because it's safe, gentle and it works well. I'd recommend administering the Rescue Remedy to both cats by gently rubbing 3-5 drops onto the outside of their ear flaps or the relatively fur free area in front of their ears at least 3 times daily, you can repeat this without hurting the cats as often as necessary. You should be able to find this remedy at health food stores, but if you have difficulty finding Rescue Remedy locally then I'd recommend that you purchase it online. You may also want to check out my previous answers about new cat introductions to ensure that you have the information to deal with any further issues that might come up between Angie and Harvey. If you have any further cat related questions or concerns, please don't hesitate to contact me again, I'll be more than happy to do my best to help you and your cats out as much as possible.