This might be kinda mean but just flat out tell her all the cons of raising a pup. They chew things, bark a lot, whine contiously (exagerrate a bit. When my friend mentionned she wanted a dog I asked if she was willing to do little things like brush him and she said no. So I exagerrated on everything - they poop a lot, they're expensive...and I convinced her not to get one) Mainly just say things that will turn her off from the idea of a dog
That's exactly what I do when a person I know can't deal with a dog, wants a dog. A friend of mine wanted a siberian husky. I told her flat out that they shed very badly twice a year, they need atleast a six foot fence, she'll have to lay bricks down so the dog doesn't dig, that huskies are more difficult to train, that they need alot of mental and physical stimulation, most don't get along well with others of the same sex, they are a bred that is known to howl, etc...I completely left out all the good things, and completely exaggerated on the bad stuff.

I don't know much about pugs, but I would tell your friend of how suceptible they are to being overweight - Tell her that the dog will need tons and tons of excersice. Also, don't pugs get bit nippy with other dogs if they aren't socialised properly? Well, any dog will atleast, so tell her how she needs to take it out for hours every day and take it around other dogs, where she could get smelly or get hair all over her lol..I'm sure there's more