I can hear dripping in the downstairs bedroom - my own - and there is an obvious wet patch (though not yet wet to the touch (fingers crossed)). The bathroom is directly above my bedroom and it would seem the area is near the sink. However, it has also been raining heavily this night. We haven't noticed it before but we're worried about what will happen if left. We're three girls aged between twenty and twenty five and we have no clue how to go about fixing something like this.

Our landlady isn't very accommodating.

First, open the vanity cabinet and look for wet spots or dripping. If everything is dry, you could have a leak in a wall pipe, drain or the vent boot is leaking. Is this is your house, apt or a rented house? If rental, call the agent or owner. If it is yours, you will need to find someone to troubleshoot the drip.