Just on whether she's broken any laws – apart from joining an illegal terrorist organisation and specifically going to Syria to help IS wage a lethal war, in the Times newspaper interview she says of the fighting that's been raging in the last few weeks in Baghuz “I was weak, I could not endure the suffering and hardship that staying on the battlefield involved” .
She appears there to be confirming that although heavily pregnant, she was actually “staying on the battlefield” (of course we might think the “battlefield” involved the entire town, such that she could not avoid “staying on the battlefield” … however, she also says that in the final few days the women were all offered the option of leaving the battlefield, and that after some time (days or weeks), she decided to walk away from that battlefield).
When asked what her reaction was to seeing her first severed head (in a bin), she not only said “it did not phaze me”, but added that “it was from a captured fighter seized on the battlefield, an enemy of Islam, I thought only of what he would have done to a Muslim woman if he had the chance”.
There she appears to be repeating the same propaganda statement that has appeared from almost every UK Islamic fundamentalist on trial in the UK (that's now several hundred of them) where almost all of them said in trial evidence or said in martyrdom videos or where they were recorded in phone transcripts etc., that one reason they were trying to kill the “kuffa” (i.e. non-believers, opponents of hard-line Islam) was because their western opponents were “killing and raping our women and children”.
Regarding her marriage to an Islamic fighter – she was aged 15 when she left the UK, and she says in the article that as soon as she got to Raqqa (Syria) “I applied to marry an English speaking fighter between the ages of 20 and 25 yeas old” and within 10 days she was married. She then had two children who both died, and now she has been pregnant with a third child of the IS fighter for nearly 9 months.
That sounds to me almost like these girls are deliberately going to the front-line battle area to instantly marry a jihadist fighter within days, and producing as many children as possible to be raised in that Jihadist battle environment.
None of that sounds to me anything at all like a person who has much if any concern that she has done anything wrong or that she needs to change her mind about supporting IS in it's campaign of worldwide mass murder.
However, despite all of that - if she is nevertheless allowed back into the UK, then afaik she is likely to be tried for terrorist offences and quite probably jailed for some years. And (according to "experts" discussing this on BBC radio this morning) her child would probably taken into state care and placed with more suitable parents who are not trying to raise Islamist fundamentalist fighters.