Patience. Tell your friend to slow down and just leave the animals
separated for a while. I assume she loved her brother and wants
to keep his cat? If so, ask her to give it some time. If not, maybe
she should hand the cat over to people who will find it a good home.

Put a screen door on the room the cat is being kept in. This way both
animals can see each other and get used to each other's visual presence
without having physical contact.  Feeding them on either side of the
door will also help them to associate good things with each other's
presence. I hope you can dissuade your friend from giving up on this
cat. These things take time and sending the cat to a shelter would be
unconscionable.  Here is more info from the cat care sciety you might
find helpful:

Dogs and cats who have not experienced each other will require some
extra time to become accustomed to each other. Dogs usually want to
chase and play with cats, and cats are usually afraid and defensive. You
can use any of the techniques described in "Introducing a new cat to
other cats." In addition:

If your dog does not already know the commands "sit," "down," "come,"
and "stay," you should begin working on them. Little tidbits of food
increase your dog's motivation to perform, which will be necessary in
the presence of such a strong distraction as a new cat. Even if your dog
already knows the commands, work with obeying commands in return for a
tidbit.

After the animals have become comfortable eating on either side of the
door, and have been exposed to each other's scents as described on the
other side, you can attempt a face to face introduction in a controlled
manner. Put your dog's leash on, and command him to either "sit" or
"down" and "stay," using food tidbits. Have another family member enter
the room and quietly sit down with the cat on his or her lap. The cat
should also be offered some special tidbits. At first, the cat and dog
should be on OPPOSITE sides of the room. Repeat this step several times
until both the cat and dog are tolerating each other without fear,
aggression, or other uncontrollable behavior.

Next, move the animals a little closer together, with the dog still on a
leash and the cat gently held in a lap. If the cat does not like to be
held, you can use a wire crate or carrier instead. If the dog gets up
from its "stay" position, it should be firmly repositioned, and praised
and rewarded for obeying the "stay" command. If the cat becomes
frightened, increase the distance between the animals and progress more
slowly. Eventually, the animals should be brought close enough together
to allow them to investigate each other.

Although your dog must be taught that chasing or being rough with the
cat is unacceptable behavior, your dog must also be taught how to behave
appropriately, and be rewarded for doing so (e.g. sitting, coming when
called, or lying down in return for a tidbit). If your dog is always
punished whenever the cat is around, and never has "good things" happen
in the cat's presence, your dog may redirect aggression toward the cat.

You may want to keep your dog on a leash and with you when the cat is
free in the house during the introduction process. Be sure that your cat
has an escape route, and a place to hide. Keep the dog and cat separated
when you aren't home until you are certain they will both be safe.

Precautions: Dogs like to eat cat food because it is very high in
protein, and therefore very tasty. Keep cat food out of the dog's reach
(in a closet, on a high shelf, etc.). Why dogs like to eat cat feces is
not well understood but it is a relatively common behavior. Although
there are no health hazards to the dog from this habit, it is usually
distasteful to the owners.

Attempts to keep the dog out of the litter box by "booby trapping" will
also keep the cat away as well. Punishment after the fact will NOT
change the dog's behavior. Probably the best solution is to place the
litter box where the dog cannot access it such as behind a baby gate, or
in a closet with the door anchored open (from both sides)just wide
enough for the cat. Always feed your dog alone. Cats should not eat dog
food as it may cause dietary deficiencies.

Megan