Hi Debbie
It is a very good idea to have Boopsie checked out by your vet just to make sure there are no medical reasons why she might have suddenly changed her behaviour towards him. If she gets the all clear make sure every time they are in the same room they both get something nice to eat or to play with. This way you can build up a positive association between the two cats. You could also try the "smelly" towel approach. This is where you take two clean towels and have one for each cat. Rub one around Boopise's neck area and the other around your male cat and place each towel under the food bowl of the other. So once again each one is building a positive association with the other. Do not try and make them interact, remain calm and if they enter the same room make it fun. Do not punish Boopise for reacting aggressively this may make things worse. If she is still reacting aggressively towards him after a few weeks ask your vet to refer you to your local qualified behaviourist. Or you could look on the APBC (Association for Pet Behaviour Counsellors) website www.apbc.org.