Okay... at a young age/toddlers, they do get night-time 'fears' and it is developmental based, and they have imaginations that we cannot extinguish. Also, at certain ages, they do 'miss' their parents.
When I was that age... I used to have my own room. But EVERY night... I would, in the middle of the night, get up, creep down our dark scary hallway... go to my parents room, and plop into their bed. They let me. I grew out of it. My older sister, would tease me about it. She wasn't like that. My parents, never made fun of me nor punished/scolded me.
It is a phase... I grew out of it.
You can force her back to her room... repeatedly. This is what is done to get the kid back in their room. Some actually lock their kid in their room at night. Or they are punished.
So, you have to decide: is this a battle you want to choose or not? Is this a big problem for you? Or is it just no big deal? is the idea that a kid HAS TO BE IN THEIR BEDROOM so absolute to you.. that you want her in her own room? If so, then you will have to repeatedly put her back in her room... and be up at night doing so, and she will be as well. Up at night at varying times, doing that. Repeatedly. Or, you scold/punish or give treats and rewards to get her back in her room.
Our kids, well we have a floor futon in our room. Our kids have their own beds. But we also lack space... and if need be, if the kids are sick or are scared or something wrong... they can sleep on the FLOOR futon, that is in our room. They don't sleep IN our bed. We don't think its a big deal. Some others here may think its a big deal. But we don't. It works for us. We never ever have night-time or bedtime battles with our kids.
And yes, when kids are sick... they get clingier.
And as far as couple time in bed... well, you can do it at other times... or some place else in the house. That is no problem and fun! That's what we do. Its no problem.
all the best,
Susan