Thank youIt really depends on the rats. I would never be able to keep my girls (adults) in a cage with 1 inch spacing (without modifications). My boys on the other hand went into a cage with 1 inch spacing at a very young age (around 3 months). I would recommend the smaller bar spacing for very young rats even if you get males. I do have a cage with 1 inch spacing for my girls, but I had to cover it with hardware cloth to keep them from escaping >.
You'll have to convince her that 2 rats is necessary since rats shouldn't be kept alone. Something I tell potential adopters that don't know much about rats is this: a lone rat is like a puppy that doesn't get played with, it will be destructive and depressed and will usually have behavioral issues. Even if you're home all day, rats are nocturnal and will be most active at night while you're sleeping, so it's only fair to get them a friend to play with.