BOS to New Hampshire contingencies
 

My sister-in-law will be arriving at BOS on a red-eye at 5.30 a.m., and planning to take the Concord Coach to meet us in Concord, NH (which isn't our home; we'll be there for an appointment). Looking at the Northbound schedule to Concord at https://concordcoachlines.com/stop/concord-nh/ , she should be fine to get the bus at 6.45 a.m.; with it not going to South Station (where pax can get off to buy tickets) after Logan, I'll advise her to book and print the ticket online before leaving home. With the hope that worrying about contingencies will keep the problem from happening, I'd like to consider "what if the flight is late and she misses it?". There's the bus leaving only from South Station, not going to Logan, at 8. I guess I would advise to take the free Silver Line bus to South Station. What is the latest she could comfortably take it and find the Concord bus, on a Monday morning? Or just wait at Logan for the 9.25 bus.

I would hop in an Uber to South Station and take the 8:00 AM. Because there is no ticket office at BOS, she may simply purchase her ticket at the first stop, which would be Concord if she is on the early bus and South Station on the later.

I would definitely not wait another 1:25 for the next nonstop bus.

(Back from a few days without power.) Good to know. The question still arises: Including consideration of the Uber/Lyft pickups now being in the parking garage, how late could she take one, get to South Station, navigate the complex that's unfamiliar to her, buy a ticket if applicable and board the 8 a.m. bus? As I understand, if she prints the ticket in advance, it's valid for later buses, and should be good for the bus from the station although she'll have paid $5 more than needed.

It takes about 10 minutes to drive from Logan to South Station. Including time it takes the Uber to get to Logan, I'd say she's fine if she's ordering it by 7:30 AM. She should tell the Uber driver to drop her off at the bus station area at South Station. If it's between 7:30 and 7:45, she still should have time to take a taxi, since there's usually no wait for those.

Also there is a waiting area at South Station should something go amiss. At Logan, you are curbside outside of baggage claim. It's worth the trip to South.