Blood “from” or blood “of”?

I would say that there is a slight difference in emphasis. "Blood from her wife" would tend to refer to blood where the route by which the blood reached the place it was found was both obvious and significant.

On the other hand "Blood of her wife" (or more usually "her wife's blood") would tend to refer to a situation where the path is less obvious or less significant.

For example if a surviving wife were to be found in contact with the body of her partner in a crashed car and the dead woman had bled directly onto the live one we might say "Alice's blouse was soaked in blood from her wife". If, on the other hand, Alice had got out of the car and was found walking a few yards away from it but still had the blood on her we would be more likely to say "Alice was covered in her wife's blood".

One circumstance where "blood from her wife" might be more common would be a case where the women had compatible blood types and Betty had donated blood to Alice in an emergency. In that case we would be likely to say "Alice was saved by blood from her wife" since the route from one to the other, although complex, is well understood and the route is significant to the account.

Having said that "her wife's blood" would be more common in almost all circumstances than "blood from her wife". I would also say that although "Blood of her wife" is perfectly grammatical is much less likely to be used that the compressed posessive "Her wife's blood". It used to be common to ridicule English/French phrase books as containing the entry "The pen of my aunt is broken" instead of "My aunt's pen is broken". This is another example of the same thing.

Strictly speaking, of can also denote possession.

If she kept a vial of blood that was produced in the body of somebody else, it could still be considered blood of hers, just as a car that she owns could be considered a car of hers.

There is such a thing as a blood fetish, akin to vampirism, and some couples will keep vials of blood drawn from the other person.

So, in the right context, the following dialogue could occur:

"She had a vial of blood on her, as did her wife."
"Do we know where the blood of her wife came from?"

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Of course, from her can also have the meaning of a gift or thing that came from somebody rather than was actually owned by somebody.

In another context, there could be this dialogue:

"Everybody received a gift of some kind. She received blood from her wife."
"Do we know if it was the wife's blood?"

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So, blood of her wife and blood from her wife can mean the same thing, but they don't always have to.

There would need to be more context provided than just the phrases themselves to know if such a replacement could be made and commonly understood in the same way.