quick question for a friend....

She's flying UA long-haul international flights operated by 747(outbound) and 777(return), has no status, assigned to exit aisle seats on both.

Which boarding group will she likely end up with? She has one carry-on and one backpack(both are under the UA size rules). Is there any chance that she will have to gate check one of them if overhead space become full? Both flights are extremely full, based on the seat maps. Do they even do gate check on the widebodies?

Thanks!