My mother in law gave me a (nice) dress & nylon underskirt but I'm sure (both) are from a thrift shop. Is this acceptable/should I wear it?

Well, aren't you a special kind ?

Most of my clothes are from thrift shops and I am always the most fashionable person in the room.

Honestly i feel like you should be very thankful she gave it to you because its people that doesnt have anything and suffer to buy things and wish they would have what you got . be grateful for everything / anything !

If u don't want it I'll take it

Thrift shops are fine to get clothes at, as long as its not underwear/bras

So? it's just a store, spray Lysol disinfected spray and wash it before wearing it. Accept the gift.

I personally wouldn’t I’d say thank you and give them back to the charity shop or bin them

You are a clothes snob. As soon as you buy a new item it becomes second hand. You need to climb down of your high horse and be grateful your mother-in-law is a nice person.

Go nude

Why wouldn’t it be?