Unfortunately yes, separating a bonded pair is not a good idea. They mate for life, and he knows his mate didn’t die. He is unlikely to accept this new female and as things are going, he is going to kill her if you leave them alone together. The best thing to do is get his mate back. You need to understand how lucky you were that they produced healthy chicks. Most people do not get that lucky, because birds are not that easy to breed. Also, changing mates may not result in other colors. It all has to do with genetics and if he is a normal green, for example, he may only produce that color because his genetics are the strongest. There is also the chance that he has something else in his genetic code, or his real mate does, and they may surprise you and produce other colors. You also need to realize there are different species of lovebirds, and different color mutations of each species. Do you know what species you have? Is the new bird the same species? You can mix color mutations, but do not mix species. If you don’t understand this much, you have a lot more to learn about lovebirds before you try to get or make another pair. Please get the bonded pair back together and if you want different color mutations, buy a new pair.
Thank you for asking Lafeber,