I think the answer partly depends on where you take Miss 1915 from and where you bring her to. A city person brought to the city is going to be a lot more familiar than a city person brought to the modern suburbs or a rural person brought to a modern city. For example, the city or town dweller wouldn’t be impressed by a modern bathroom while a rural dweller probably still would be.
Apropos of nothing, walking from the train station to my office the other day I contemplated just this question (anthough not specifically 1915).
“Because by 1915 we had aquired the concept of progress, and she would be expecting 2001 to be full of strange technological wonders. That would make it much easier to adapt than for someone who expects the future to be like the past.”
That was my basic thought. The 1915 city dweller probably wouldn’t be shocked by city traffic, because they had lots of traffic and they had automobiles, they just didn’t have lots of automobile traffic. 
With wireless telegraph already well in place back then, plus the ETERNAL competition of news outlets to be first, I don’t think instant news wouldn’t have been such a shocker either. Instant moving pictures of news, maybe, but not instant news itself.
“She’d be flabbergasted at the telephone. Telephones were monstrously expensive, inconvenient devils in 1915, and most
families wouldn’t have seen much use for them since they’d regularly see everyone they wanted to talk to anyway.”
I don’t think so. This is another urban/rural thing. IIRC, by 1915, the Bell system had already instituted its famous 5 cents a day phone charge that caused millions in cities and larger towns to subscribe. Long distance was expensive and slow, but local calls were not even charged individually back then, since the paperwork of doing a slip for each call was prohibitive. The traffic was so great that there were already experimental dial exchanges by 1915, and regular dialing in big cities like New York and Chicago came less than a decade later. A phone by 1915 would probably have been considered like a cellphone or fax now – a business person HAD to have one, and the average middle class person considered it a VERY useful convenience even if not a true necessity.
“…the crowds. Most of us now live in cities; there just weren’t six billion people in the world then.”
I think that crowds would be about THE LAST thing that would surprise Miss 1915, at least if she were a city dweller brought to the city. If anything, considering suburban growth since then, urban crowds were probably bigger back then. Lower Manhattan before the subways moved people out to Queens and the Bronx was the most densely populated area of Earth EVER. Denser than the densest third-world slum today or the densest high-rise neighborhoods of upper Manhattan today. Or a more mundane example:, if you were middle class and went (non-food) shopping, you pretty much HAD to go downtown on public transportation to the big department stores. Millions of people still do that in many cities, of course, but millions of others drive and use suburban malls.
“This is often advertising, of course, and it jingles and glitters and pervades our city world in a way that it just didn’t in 1915. Packaging and billboards, for instance.”
I don’t know about how colorful advertising was back then, but it was pretty much as pervasive as it is now. Looking at pictures from then, subway and elevated stations were filled with ads, omnibuses were covered in advertising placards just as motor buses are now, and buildings along busy streets in cities positively dripped with signs. Newspapers lived off advertising, not sales, revenue as much in 1915 as today – hence the penny newspaper, which didn’t cover the cost of gathering and printing the news but upped circulation so that advertisers were willing to pay rates that DID pay the bills.
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