Did she say WHY to give up the night light?? I would continue using it, for sure! Your reasons are completely sound, plus I'm a sucker for home decor and you've found a neat way to add to the room! If the light was actually in the bathroom it would be no different because it would still cast light into your bedroom. I would not worry about this and wouldn't let your T make you feel bad or childish for it.

As for the office...there are two big age groups for when 'character' or 'childish' things are acceptable. The one and only time it's frowned upon to have such things is the dreaded tween/preteen/early teen years. Of course before those years it's acceptable, and then around age 16 or so it's suddenly 'cool' and acceptable and 'cute' again. Of course it's really acceptable at any age, but those tricky years are when your social group would likely torture you over it. At 40 years old you are well past being mocked over having such a collection so enjoy it and don't let your T dissuade you.

ETA: Also, I wouldn't make a big deal out of defending these things or anything. I would act like SHE has the problem for having a problem with any of it. Act puzzled as to why on earth she is focusing on a LIGHT that allows you to not trip on your way to the bathroom, or items you COLLECT, not play with. Seriously, act like she has the problem and you're concerned about HER...