It does not follow that she will be dismissed particularly if there is an alternative option available. At the meeting she can be accompanied by a trade union official or work colleagues, she may though find work colleagues do not want to get involved. I do not know what the mistake made was or the previous errors but the employer may decide it is capability, which is one of the five potentially fair reasons for dismissal. I would suggest she considers the error she made and the reason for it and how she can make sure the chances of it occurring again are greatly reduced; if she genuinely believes that being told she was pregnant was a factor in making the error she should present this at the meeting. If it is decided at the meeting she should be dismissed she should be notified that she can appeal the decision, if this fails her remedy is to claim unfair dismissal at an employment tribunal, but make sure of time limits.