I like the implied threat in the last statement: "before she saves you". How long is "before she saves you" and ""you're probably going to die"? Is Mom going to save her son first then straight away save his girlfriend, or wait...
And as she is the person who is forcing her boyfriend's mum to learn to swim in the first place, I don't think Mom is going to look favourably on her. So yeah, odds are pretty good, she's going to drown.