Hello again, and thanks for your reply with additional information about your kitty.
She does sound adorable! If she's comparatively new to your home, she's still adapting to her new environment, so it's not surprising that she feels a little insecure when you have company. She's first getting used to YOUR scent and surroundings, and then when she smells 'new' people, hears other voices, noises, etc., she gets a little apprehensive. This is common feline behavior, and some cats have personalities that are more timid than others; some are bolder and seem fearless. If you have a 'scaredy cat', that's alright, as long as she always has a 'safe' place to hide, when she's startled by a noise, or feels insecure, like when company is around.
She might outgrow this behavior, but for the moment, I'd let her be, and allow her to feel secure under the bed, as long as she's still emerging, after your company leaves.
Your cat might benefit from a cat appeasing pheromone called Feliway/Comfort Zone for Cats, which comes in both a spray and plug-in diffuser. It's available at major pet supply stores, and also online. The diffuser resembles a plug-in air freshener, but has no scent to humans. Feliway helps to relax stressed or anxious cats, and is useful in a multitude of situations. For more information, please see: www.catfaeries.com/feliway.html
She will most likely become a little more comfortable as time goes on, and might be less skittish with company and as she gets more used to the usual noises in your home, but I wouldn't press her to come out and be social, if she's frightened. When your company leaves, be sure to make her feel reassured and secure (which I'm sure you're doing), and hopefully, she'll appear less timid in the future.
She does sound like a lovable furry girl, and I wish you both much good luck!