This is still very common - and it is called a "gate pass". However, it can't be done for international arrivals.

To anwer other questions raised...

Yes, it is very common to tip the person who helps her with the wheelchair. If she has limited English capability, it can be very useful for her to have a sheet of paper with alternating paragraphs (in her language and English) with all details of her travel, including your phone numbers.

Be sure that she knows to follow the ARRIVALS signs when she gets off the Austrian flight. That will get her onto a mobile lounge that takes her to IAB in the west end of the main terminal. (If she follows the TRANSFERS sign, she will go to the immigration facility in the C concourse for connecting passengers - which is a real pain to correct.)

In the IAB, she will first go through primary inspection, aka immigration/passport control. Then she claims her checked bags from a carousel (there are free baggage carts there - don't rent one while waiting for her). Then she passes secondary inspection, aka customs. Then she exits the IAB area into the west end of the lower level of the main terminal (aka the arrivals level, aka the baggage level). That is where you wait for her - just past carousel 14; very close to arrivals door # 1; a few steps from the Starbucks and restrooms. And, yes, there is a Travelers Aid information counter right there to answer any questions - it is set back a bit, but has a well-lit sign above it.