You can talk about it. But if you post anything that creates "a substantial risk of serious prejudice" to the trial, you risk facing proceedings for contempt of court. And the law has now been changed to allow fines to reflect the amount of public money thrown away if a trial has to be abandoned. Which would be loads.
Realistically that risk will be created most easily if you post something about this woman not previously in the public domain that would lead people to think she must be innocent/guilty. The classic example is revealing someone's previous criminal record (not saying she's got one, that's just an example), or stuff the jury might not be told for whatever reason. A good example of that is the Mirror article during the trial of footballers Lee Bowyer and Jonathan Woodgate for assault, accusing them of a racist motive (the assault victim was Asian) when the trial judge had said there wasn't enough evidence to back that up and it was not to be put to the jury. The Mirror got fined rather a lot of money.
Also, although every individual feels they have a right to post their opinions, if 100,000 people are all shouting someone's guilt or innocence from the rooftops (ok, their keyboards) it does create an atmosphere that makes a fair trial more difficult. Look at that Colin Stagg bloke. The whole country decided he had obviously killed Rachel Nickel when in fact, no he hadn't. Colin Jeffries etc. He wasn't on trial, of course, but the dynamic is the same.