Still, it would make it easier for me if I could understand her perspective better. Can anyone here offer some insight/opinions on the questions above?
I think it’s great that you are trying to understand her perspective. Certainly, as others have pointed out, marriage does involve a bit of going along even
without understanding.

Still, it’s good to try to understand what we can.
There are two main reasons that a Catholic might give for wanting separate overnight accommodations in these scenarios: (1) occasion of sin; and (2) scandal.
For some, being alone together in certain situations presents an occasion of sin—a temptation to choose something that is wrong. Different people will have different levels of comfort here. Some are better than others in controlling their impulses. For me, I think it’s best to find the middle ground between “There’s no way an unrelated guy and girl can ever be alone together without succumbing to their passions” and “There’s no way I could ever be influenced by my passions, so why bother taking reasonable precautions.”
It is reasonable and prudent for Catholics and those striving to live out their call to chastity to set boundaries. Now, maybe one person would prefer to err on the side of caution whereas someone else doesn’t find it necessary to be as cautious. I think in general we tend to be more likely to overestimate our capacity for self-restraint rather than underestimate it. Or maybe that’s just me.

In relationships, I think it best to defer to the one who is more comfortable exercising greater caution.
Second, such overnight situations are potentially a source of scandal. Now, by “scandal” I don’t mean that it will cause little old church ladies to clutch their pearls and simultaneously gasp in astonishment while also wagging their fingers in condemnation. To cause scandal is less about “shocking” people than it is to make it easier for another to sin.
So in these types of situation, scandal can result if, say, your girlfriend has a younger sibling who sees what you two are doing and then assumes that it is okay to spend the night at
her boyfriend’s house in any and all circumstances
without being concerned about practicing chastity. Or maybe her sister or her boyfriend don’t have the same self-restraint the two of you have. Your action here could “lower the bar” of acceptable behavior for the whole family and make it easier for others to find themselves committing certain sins. That would be a scandal.
Now, there are some Catholics who would argue that—in our current culture where many assume sexual activity is taking place in any dating relationship—staying overnight with your girlfriend will
always be a scandal. There’s a case to be made for that position, but I think there is room for other points of view from a Catholic perspective.
(continued in next post)