There are no hard and fast rules or beliefs when it comes to spirit interactions, so how it happens and what you should do will be largely influenced by your own beliefs.
I believe that spirits can travel the Earth just like we do, moving freely from place to place whenever they want. They aren’t bound by the physical laws of the world, such as solid objects, space, and time, and therefore might have found themselves in your home by mistake or on their travels.
I also believe that spirits can be tied to objects, places, and people. This can be a choice they make or one that is made for them depending on the nature of their spirithood. For example, I believe that a spirit who was once human but died tragically may find themselves tied to the place of their death. A person who died and wasn’t ready to move on may find themselves tied to a place or favorite object.
Spirits may also hitch a ride with living people, attaching to our energy and using us as a sort of public transportation system and energy source. This can be done with malicious intentions or it can be done for the sake of convenience - maybe they just like you.
Then there are non-human spirits. These are spirits that were never corporeal, who never lived on Earth as a human. These spirits may include land spirits, deities, transient energies, plant spirits, etc. There are too many non-human spirit categories to list, but the general point is that spirits aren’t necessarily people who have passed on.
She may not have “revealed” herself, so to speak. Your husband may be more prone to seeing physical manifestations of spirits while you are more prone to sensing them. Spirits can reveal themselves to us for any number of reasons. They may be looking for help, lonely, bored, etc. They don’t often have the same motivations as living humans, but they can.
As for if you should do anything about it, that’s entirely up to you. Personally, I wouldn’t try to cleanse a spirit from my home unless they were affecting me in a negative way. As @georgia said, the easiest way to figure this out is to try communicating with the spirit. She may not communicate with you, but trying is always a good option.
It’s possible that this spirit just wants you to know she’s there so you don’t freak out if something happens, such as opening things or moving things. She may have a message for you, or she may be looking for company. She may not want any of these things and instead wants to exist in peace without being bothered.