Go back in time and don't let her in your bed the first time ;) just kidding.
i agree, try the super nanny thing, where you put her back in bed. after the first time, don't talk to her, just do it. if she goes to bed ok at her bedtime, she should be fine. you just have to make the decision to not let her back in. she may cry, but it won't be more than a few nights if you're consistent. she might surprise you, she may not even be bothered by it. kids do what we allow them to, so she may just think it's ok, even though you tell her not to come in, you still let her in the bed, so she's probably just trying anyway.
if you think she's having to pee, then stop all liquids after dinner. that might help.