Hello, my name is Dr. Kara and I have over 20 years of experience as a veterinarian.
I am sorry to hear that Lucy is behaving so poorly toward her daughter but her behavior isn't unusual.
Cats don't live together normally in the wild. They have territories, although they
are fluid, and will fight to preserve resources. In the wild once kittens are old enough to hunt, and certainly by puberty, the queen will chase them out of her territory. She does not want more kittens interfering with her resources, which a daughter would likely produce given time. In many cases with unlimited resources in a home environment they learn to live together peacefully and some learn to enjoy each other's company. But some cats simply never learn to tolerate other cats in their environment. It is worth trying to get them to get along, but it may not work.
She probably doesn't bother your male because it was his place first and many time a female will tolerate a male better then another female.
Do they ever ignore one another and co-exist peacefully while in the same room or
does she react every time she sees her daughter?
At this point I would never leave the two of them alone together when you aren't
around to mediate. And in fact you may want to start over with introducing
them again once the kitten has been spayed and has had time to heal, as you will likely have problems when the kitten comes home smelling differently after her spay.
In aggression cases I recommend using a product called Feliway, so I am glad to see that you are using it. It is a synthetic version of a feline calming pheromone.
There are also pheromone collars which may be helpful for Lucy. It's worth a try. See
this link: http://www.amazon.com/s/ref=nb_sb_ss_i_1_17?url=search-alias%3Daps&field-keywords=feline+pheromone+collar&sprefix=feline+pheromone+%2Caps%2C197&rh=i%3Aaps%2Ck%3Afeline+pheromone+collar&ajr=0
Keep them completely separated, behind closed doors until your little one is healed after her surgery. That way they aren't constantly confronting one another but are able smell and hear one another and get used to having each other around in a non-threatening manner.
Make sure to frequently switch bowls, beds, toys and use the same brush on both
cats to get them smelling the same and familiar to each other.
Then try using a large baby gate between areas to keep them separated from each
other but able to see one another for a few weeks. If she is becoming aggressive
at that point with her daughter then you may want to try a homeopathic calming oral medication called Bach's Rescue Remedy. See this link for further information: http://www.bachflower.com/rescue-remedy-pet/
We want them calm enough to learn to at least co-exist.
If things are going well allow them in a room together, but only when you are present.
You should make sure that there are plenty of spots for both cats to get up and away from each other, such as cat trees or ledges that are carpeted and comfy to sleep on. Cats do tend to get along better when resources are unlimited. Make sure there are plenty of toys for everyone and don't let Lucy harass her daughter. If she isn't
respecting her and does chase her or continually tries to approach her it's fine to use a can of coins to throw near her as he approaches her for negative reinforcement.
You may also want to feed them separately in different rooms so neither feels there
is any food competition.
If all else fails discuss anti-anxiety meds with your veterinarian like Buspirone or Amitriptyline for both of them as stress is certainly playing a part in this. If either one hates taking pills there are transdermal gel formulations of these medications available.
Finally she may do better when allowed to go out so you may wish to construct an outdoor cat pen so she can safely spend time outside away from her daughter. Here are some examples:
Best of luck with this situation, and let me know if you have any further questions.