Hi Cin,

The obvious answer is to ask your RSPCA contact for advice.  You will
certainly need two litter trays, two wet food dishes, two dry food dishes,
two water dishes.  At first they will need separate toys.  Eventually, they
will share these .. but in the meantime support each cat's right to its
possessions.

From personal experience,when you introduce them I would suggest you close
all doors and windows!  Bella is quite likely to spit, scream and scratch
and explode in every direction.  She will feel SO betrayed.  It is essential
that you hug her most, not Bonnie, and reassure her as much as possible.
Explain/insist that Bonnie is there to live with you both and that she
(Bella) will have to get used to it.  Encourage contact, but do not force
it.  The multitude of hiding places is very useful (as much for Bonnie as
Bella) .. but no cat wants to spend its life hiding.  From now on, Bella is
No.1 cat.  Call her first, put her dinner down first (only seconds before
Bonnie's - you don't want to tease the new cat).  Praise Bella for entering
a room where Bonnie is .. scold her gently if she then spits, etc.  Whatever
else you do, don't allow Bonnie to do something you have never allowed Bella
to do.  House rules (if you have them) must be equal for both cats.

This may take many weeks and heaps of patience.  My Cheetah hated Panther on
sight and made no secret of it.  I proceeded as above (I already knew it
worked - done it before!); I also made special time for Cheetah when Panther
was in a different room so that she still felt wanted by me, and special.

After some weeks together there was an improvement.  The big catalyst for
mutual acceptance came after they were parted for a week (one in cattery,
one with Cat Rescue).  They missed each other .. or the rather hostile
playfighting!  Even after 6 months there is still some jealousy (there
always will be), but they play together, playfight together, eat together ..
even sleep together on a cold night.  Just try and understand how each cat
feels, and be very patient.

NB:  After a bout of fighting, check each cat for injury - especially eye
injury.  Most important of all: always check Bella first.

As to the name change, if you must change it, try and keep it similar in
sound .. like Donnie/Donna.  If that doesn't suit, combine the old and new
name.  For example, if you decide to call her Tiger, start by calling her
Bonnie Tiger.  Keep this up for some time, then increase the Tiger name.  It
helps that Bonnie is an adjective.

Good luck.

Spider