The flifo available in ExpertFlyer shows that they held briefly for connections. Whether this is in any way related to what LH told you, I don't think anyone can say.
0927/01DEC
P FRA/OUT 539P L00.14 EST OFF 558PCONNECTIONS
P FRA/OFF 557P
P SFO/ETA 809P L00.04
SKED FRA ORIG 525P GTD Z25 SHIP 3021
SFO 805P TERM GTA G13
FlightStats shows that at 17:31, the ETD changed from 17:25 to 17:35. How accurate that is compared to UA's internal systems I don't know, but extrapolating from the two sources, one possibility is they held for 10 minutes and that was it.
So sorry to hear about your wife's condition...sending prayers to both of you.