I had twins by IVF (in my early 30s). I agreed to the standard policy of having two implanted, because we were told the chance of getting a take home baby was 14% - so I really did not expect it to work.
I can honestly say I had no idea what twins would be like, and I had one already! So, this woman cannot be blamed IMO, for not knowing what she was getting into!
As a friend, my advice to you, would be to offer to go round and just spend a couple of hours looking after one, when you have time. Looking after one, when you are used to twins is a rest cure! What I really missed was having 1:1 time at feeding times/mealtimes, instead of always having divided attention. When they are walking, help take them to the park - it’s really hard when they run off in different directions, because they are both lacking equally in any sense. You can tell an older child “Stay with the buggy, while I run after DD1....”
Probably the thing that would help the most, would be if you could look after both, after they have been fed and are hopefully asleep, while she has a nap in the early days, because lack of sleep is the worst - but you may not feel confident doing that?
Advise her to get the flu jab, because it is really hard with flu, looking after twins; and be careful about use by dates, shellfish, etc - don’t take risks with getting food poisoning, as that is really hard too!