I think the amount you do during pregnancy needs to reflect your own level of fitness and ability riding. We have a number of top british equestrians who are known for having continued to compete during pregnancy - this includes jumping huge (think as tall as a person) fences in competition, and galloping at speed.
It's really hard for any of us to say what our opinions are of her situation, as we don't know her or the horses she is around.
Personally I rode until I was around six months - mainly stopped as I could no longer get off, not even jumping down with leg over neck. But I did scale back what I did before that, and which horses I rode. So I rode my sensible anybodys ride cob, pretty much as usual. I rode my slightly sparkier mare in the arena only, and didn't jump. And I stopped riding my pony who bucked for fun entirely - although she'd never got me off, I didn't think now was the time to find out she could.
On the whole, the rule of thumb is that if you've always done something, you should be fine to continue, as long as you feel fit, healthy & comfortable.
I continued to muck out & poo pick paddocks right up until I gave birth, pretty much. The day before I went into labour, I was at a horse show (just on foot). And three days after I had my daughter, we all three went to a horse show - again, just on foot. Five weeks after having my daughter, I was back in the show ring with a pony. But then, this is my life, it's what I do. So this was right for me.
I've known people give up as soon as they found out, and also known people continue right up until they gave birth. Neither are wrong.