Very difficult to tell from that description, unfortunately. IMO, highly unlikely that a bad O2 sensor would cause that but anything is possible. When you say it won't start, does the engine have enough juice to turn over? I would assume not since they tried jumping it. How old is the battery? They eventually give out. First thing I would check is to make sure the battery cables are tight on the terminals and that they aren't corroded. Very easy to remove, clean, and reinstall them. Multimeters are very cheap and there are a ton of Youtube videos on how to check the battery voltage while the cables are off. It's very easy to do. That's where I'd start. If the battery is low, then charge it if they have access to a charger. If it won't hold a charge, then the battery may be bad. Any auto parts store can test the battery too if you remove it and take it to them. If battery is good, then move on to the alternator. If they can get the HL to an auto parts store, the store can load test the alternator to see if it is charging the battery. If they have a way to read the codes via the OBDII port, that would give them even more clues. Most auto parts stores will read and give you the codes for free but, of course, you need the vehicle there. You can buy OBDII scanners at all price ranges too.
If the vehicle can't be started and will have to be towed anyway, might as well take it to a shop as mentioned. I guess, it just depends on available funds and how comfortable someone is troubleshooting stuff as to which path to take (DIY or shop).
