Morphine can't help any performance, since there are multiple collateral effects, that affect any kind of activity.
I don't know why it's in the list of not allowed medicines : I think is in the list because very dangerous for the health, and one of the goal of antidoping is also to protect the health of the athletes.
Lucy Kabuu is 35 years old, and had a very long career, going in the final of 10000m in two Olympics (Athens 2004 and Beijing 2008). She was based in Japan, and was managed by Ricky Simms.
After a long period with tendon problems, she moved to marathon starting the preparation in the summer of 2011, and changed manager going to Gianni Demadonna. In that period I was her coach, and she impressed me for her quick improvement.
Her first marathon was in Dubai, and she was second in 2:19:34 (28 Jan 2012). She was still with me in training till London, when was 5th in 2:23:12 (22 Apr 2012), showing probems of full recovery after Dubai.
After that marathon, she was coached by Gabriele Nicola, at that time coach of Mary Keitany, till 2015.
Lucy had many problems in the following years : she divorced, and had several injuries, quitting running.
She changed management, going with Federico Rosa, and started running again in the summer of 2017.
Her last two marathons were the slowest of her career :
2:19:34 (2) Dubai 28 Jan 2012
2:23:12 (5) London 22 Apr 2012
2:22:41 (3) Chicago 2 Oct 2013
2:44:26 (24) Moscow 10 Aug 2013 (WCh)
2:24:16 (3) Tokyo 23 Feb 2014
2:20:21 (3) Dubai 23 Jan 2015
2:31:21 (6) Hong Kong 21 Jan 2018
2:27:02 (1) Milan 8 Apr 2018
It seems very clear that her doping was due to some mistake in some medicine, and not for the idea to improve her performance. I never heard of somebody using morphine for running faster.... but for running slower !
However, her excuses are ridiculous, since morphine is not a substance used in some supplement (like, for example, some steroid in small quantity, that we can find in medicines made in India/China/Pakistan, and clearly show that she doesn't know anything about medicines, and that the administration of that medicine was not administrated by persons involved in the management (somebody can really think that dr. Rosa can give morphine to an athlete who has to run a marathon ?)
So, a clear doping for ignorance, and I don't find correct she can considered a cheater, while is correct she has to be banned because using something against the rules, not because had some advantage, but because was not professional trying to understand the components of the pharma.