I used to be the “poor friend” in some scenarios, as well as the “rich friend” (although I’m not rich by any means). Sometimes you just feel like going to a fancy place and ordering something other than the cheapest drink, BUT you should always confirm with your friends it’s okay. I, personally, have no issues talking about money. Right now I’m making a decent salary, but I’m also saving for a down payment. My friends know it and if someone offers to spend $50 on a steak, I remind them I’m on a financial diet and order calamari. :) Or something even cheaper.
Also, it’s borderline disrespectful to invite your friend, who either has a financial hardship or is saving money foe whatever reason, to an expensive event. If I told someone I’m not spending money right now and they invited me to a fancy restaurant, I would probably disengage with them after a few instances like that. They aren’t your friend if they fail to listen to you and acknowledge your financial situation.