I'm 49 year old,bike it's been my dream for many years,and never I've drive a bike before my actually speed,my opinionin is ,isn't bike the problem but how you use bike .
if your choice is go on for relax and not for run as a crazy,ther's no any problem,speed in a iron sweet, agreable,but she can run,it's only your hand that decide how to go.
ride safe,it's a good choice.