Xkcd dating age chart
Many people – myself included – have experiences where they have successfully gotten a number or a date or what-have-you from a bartender, a waitress, someone they met on the bus or the train. You can’t bank on people explicit indications that she’s interested in talking to you… It’s better to “miss out” on an opportunity than to end up being yet another warm body in the asshole conga-line of her day.
Now an obvious caveat: people are people and everyone sets their boundaries where they see fit.
There will always be exceptions to every rule and people who may be receptive to being approached under these circumstances.
Graph of the Half-age-plus-seven rule ("never date anyone under half your age plus 7"), which claims to dictate what age disparity between two people is acceptable in dating/romantic/intimate relationships during the late 20th century / early 21st century (called the "Standard creepiness rule" in the xkcd webcomic).
According to this rule, the age of the younger person should not be less than half the age of the older person plus seven years, so that (for example) no one older than 65 should be in a relationship with anyone younger than 39 and a half, no one older than 22 should be in a relationship with anyone younger than 18, and no one under 14 years of age should be in a relationship at all...
If you want to ask her for her opinion on the Jim Butcher book she’s reading, the you can wait until she’s put the book down, rather than plopping yourself in in the seat next to her and demanding that she pay attention to you.