Story doesn't make sense.
Why does Thailand care about someone living in the country with mental health benefits, and spending that into the economy, no, this would only make sense under the following reasons.
1) UK Government have asked for aid in returning her to the UK, extradition in this case wouldn't be something that would likely pass muster in the Thai judicial system, so the Thai government (who can't willy nilly revoke - would go through judicial appeals) merely waited it out.
2) She forgot to renew her visa or was made aware she wouldn't be able to (in neighboring country) one of the so -called bad guys - thus she thought she'd remain in Thailand, as there must be a reason it wouldn't be renewed, logically she should have gone to a neighboring country but didn't, thus when she didn't renew they arrested her for having a expired visa / permit to remain.
Outcome -> observe what happens when she gets shipped back to blighty.