Yes this a false widow (Steatoda nobilis), looks like a juvenile as it still has quite stripey legs (they become more even coloured when mature). They're nowhere near as fearsome as they're reputation, actually quite skittish & most likely to bolt for cover when faced with a human. However, I'm not keen on them wandering about the bathroom (or bedroom) as there's more likelyhood of them being stepped on, or finding their way into towels/clothing (bites are often the result of a spider being accidentally squashed against the skin).
I'd pop it outside, though I'm tolerant of females that build webs up & out of the way in other rooms, as they tend to stay put & you can see where they are then. But again, if their presence troubles you at all, pop them outside.
Follow the this link for a balanced view of false widows: