Sorry Maria! I looked in all the featured ad's sites and this is all I came up with. https://www.gigabyke.com/
If you want a gas powered bike you will have to buy a kit and do a build with your own bike. I guess there is no equality when it comes to motorized bicycles.
For electric it would be easy as you're just replacing the hub, gas I don't see many options for a women's bike as the frame is usually not compatible without fabrication. There are a lot of threads about selecting bikes here that may help though.
Gas engine for a Woman's bicycle.
A rear mount friction drive would be perfect.
While I don't know where you can buy a complete woman's gas powered bicycle.
I do know where you can buy the Gas motor rear friction drive kit.