I'm not sure what to do for the best in the future.
This is the background
I have a friend who is very sweet and kind, and therefore quite a different personality to me with a different parenting style and general outlook on life. We possibly wouldn't naturally have become friends if we didn't live near each other with DSs the same age (5 yo), but I very much value her friendship nonetheless.
Her DS has recently been going through an aggressive stage, which is fine, I think most boys do. My DS has just (mostly) come out of his aggressive phase. My DS used to get frustrated and lose his temper and hit out without caring who saw him. Her DS is very bright (sometimes floors me in an argument) and very concerned with being "good" and usually checks to make sure his parents aren't looking before thumping/kicking/pushing over. But he's not being bad, I'm not criticising him at all, he's just being a 5 yr old.
This is my dilemma.
Our DSs go to the same school and today we were both at the birthday party of another boy. They were in a circle for pass the parcel and the birthday boy was sitting in a soft plastic tub thing and her DS was telling him to get out and sit in the circle. Birthday boy refused and her DS started to rock the tub, putting a fair bit of effort into it. The birthday boy fell over and cried briefly but no real damage done. It was very quick, he went over on about the third heave so although a few other parents saw what was happening the didn't make it over in time to stop it.
My friend was sitting beside me but with her back to the circle so she didn't see. When the birthday boy cried she looked around and said "is he ok" and I said "he's fine, your DS just pushed him over but he didn't fall far".
I really didn't think it was a big deal and if it had been my DS I would either have given him a first warning or taken him out of the game for one round and then put him back in away from the birthday boy. My friend took her DS away into the house and when she came back she was very upset because her DS was refusing to come back to the party. He was distraught that he had been accused of pushing the other child over when, in fact, the child had been leaning out of the tub and over-balanced. I feel terrible that I upset my friend so much, she seems quite stressed and easily upset at the moment and tbh the actual incident was such a storm in a teacup that it wasn't worth my while having said anything.
Should I just let the whole thing go, or should I apologise, or something else? In future (we and the DSs go to quite a lot of parties/school things so see a fair bit of each) should I just turn a blind eye? In the past she has intervened when my DS has been up to no good, and I'm glad that she has. I have done the same thing with her DS, ie separating him and another child when they are fighting or when I have seen him about to hit/kick and she has always seemed fine with that too. This is the first time that I've tattled though.