If OP is due anything it is from HO. Anything UA did was a courtesy and OP's friend ought to be grateful not looking for more.

This was booked on .com. Therefore, it is not a consolidator ticket and it is presumably a single ticket as it is not likely possible to book a single ticket xPVG on HO from a US-based account. Presuming that this is a single ticket SFO-BKK with an interline connection at PVG (alliance / partner is irrelevant) and the connection is above MCT although tighter than one might wish, the convention is that if UA caused a misconnect, it is for UA to reroute the passenger.

But, UA did not cause the misconnect. OP made it to the HO check-in. Whether having the agent wander off with your passport for 5 minutes bringing one past the checkin deadline of T-60 matters under Chinese practice is a debate with HO and Chinese authorities and has nothing to do with UA or US law.

But, either way, HO rebooked the friend. There is no requirement that HO rebook onto another carrier (and certainly none in the UA COC or US law). In addition, no requirement that UA handle hotel or further rebooking. But, UA did.

That ends the issue of UA compensation.

This then gets to the what could the friend do differently:

First, don't wait until later to ask someone such as OP who knows what they are doing. If you are not experienced, ask first. To be blunt, this was not a smart connection to book. Perhaps it was cheap or convenient, but it was not smart. Someone experienced in flying this route, would have warned the friend off this choice.

Second, when HO changed its schedule and UA notified the friend of the new connection at PVG, ask someone who knows PVG what all of this means. 1:50 with a 60-minute check-in is rough and well below the SCT (Sensible Connect Time). Again, if the ticket is a significant savings, maybe. But, understand the risk.

Third, what was Plan B? If there had not been a kind stranger what was OP's plan if there had been bad weather at PVG, if there had been a 2-hour delay, if OP had been ill or any number of other things had gone wrong? It is one thing to make a domestic connection in the US, but backup plans are critical especially if one is not experienced.

Fourth, all of this would likely have led to the "don't transit PVG"

Bottom line here is that OP misconnected at PVG and UA voluntarily stepped up. Leave it alone.