Thanks for the additional information. It is helpful. I suspect that Lucy has recently decided that she is the boss and as the boos, it is her job to reprimand Lola especially since Lola is older and likely to be having some health issues making Lucy feel she is the best choice. It may have been that Lola was the established boss before. However, when you were in the hospital, there may not have been strong leadership from Lola and you were not there to be the ultimate boss.
When there is a change in leadership in a dog pack, the new leader often feels like any slight or disrespect needs to be reprimanded. As the new alpha, she would feel like she should be fed first, get attention first and get to be on the bed with you first . Lola would only be allowed attention, treats and to sleep with you when Lucy indicated it was ok with her. You can help a change in leadership by recognizing that the younger female is now the boss. Treat her that way. Feed her first, give her attention first even if Lola happens to get to you first. If you give Lola attention first, Lucy will likely reprimand Lola with a nip or even a fight. This sill also help Lola see that you recognize Lucy as the leader. If you continue to treat Lola as the boss, Lola will feel like she is and Lucy will feel the need to reprimand her even more.
Start obedience training with them. It doesn't have to be a formal class, but training needs to be formal in that it should be the same times every day and structured.
The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
Additional training can also help. Both dogs should be leashed and if one dog even looks at the other dog, a correction should be done. Any sign of aggression including a prolonged look, hair raised on the shoulders, a growl or even a stiff legged walk, should be corrected. A correction is a quick tug of the leash and a firm low toned "NO". Once you have done this couple of times, you should notice the dogs ignoring each other. When that happens, you will want to reward them for the desired behavior. Again, use tasty treats like the hot dog slices. This teaches the dogs that you WILL not tolerate fighting in YOUR pack.
Your hospital stay likely triggered the change. I want you to also study body language. It will allow you to understand how the wrong tail position might cause a fight to occur. Read about body language here:
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have .