Alcohol lowers inhibitions. Which is why drunk people might do things they wouldn't do while sober. Sounds like she had a fight with her boyfriend, was upset, picked up this suspect, then perhaps regretted it soon afterwards and asked him to leave (assuming there is any truth to what the suspect claims).
That's how I see it, too.
Here is a reconstruction of events (from the Italian newspapers), and a sequence of events according to Diaw:
- around 4 am: the suspect (Cheik Diaw) leaves the 'Sweet Sugar' and takes a cab/taxi to 'Montecarla' club. He is ''already drunk'' (so he said to the police). Ashley Olsen also arrives in 'Montecarla', with her friends Jade Moss and James Bateman. There they meet with some other friends and acquaintances.
Cheik (according to his statement to the police) meets three girls (in Montecarla club), one speaks Italian, the other two speak English. He offers them a drink and starts talking to the girl that speaks Italian. That one is Ashley. They are later joined by the other two girls and an Albanian: "He has delivered cocaine to the girl who spoke Italian and whose name was Ashley and she offered me some coke".
Jade Moss sees her friend talking to the black guy and warns her that he is "a bad person." They start fighting. Moss goes away by taxi.
6 AM: (according to Cheik) Ashley invites him to go to her place. "I didn't want to go, I was sick. She insisted." (By 'sick' he means he wasn't feeling well due to all the alcohol)
6.30 AM: Cheik and Ashley leave Montecarla together. The bouncer of the club, Issa Diuf, corroborates this. "Statements and photo recognition - says the police - are extremely reliable. Diuf knows Cheik, and is able to recognise him without any problems."
6-7 AM: street camera images viewed by police show Ashley and Diaw walking down 'Via dei Serragli' towards the intersection with St. Augustine street and into S. Monaca street where the Olsen house is".
7.15 AM: (witness) sees Olsen enter her apartment "with a very tall black boy." Statements that are corroborated by the images of street surveillance. The young man with Ashley wears a jacket, jeans or dark pants, black trainers with white soles: the same are seized by the police in the search of the house where the Senegalese lives with his brother (via Andrea del Castagno 41.)
7:30 AM (from Cheik's statement) "We drank and snorted coke that she had in the house. Then I went to buy cigarettes. I came back. Then we had sex, after which I went to the bathroom and threw away condoms and a cigarette butt. Then she told me to 'go away' because her boyfriend will come. She treated me like a dog. She pushed me and hit me on the side. I pushed her back and punched her. She fell, got up, started to push me again. Again I pushed her, she fell to her back and banged her head on the floor. I took her by the neck and pulled her up. Then I carried her over to the bed in the loft. She said she wasn't feeling well. I was drunk and had taken cocaine, but I didn't strangle her."
8.30 AM: Cheik exits Ashley's house (so he claims)
9-11 AM: the neighbour of the victim hears "muffled screams"
9.20 AM: Ashley's phone dials 11 ("perhaps one last effort - say the investigators - to contact 112, 113, or 118 - probably the last and desperate attempt to call one of the emergency numbers)
14.31 PM (and up to 23.31): the police, through phone records, found out that for nine hours Diaw's SIM card has been inserted in the phone of the victim.
I wish that the English speaking newspapers would translate more from the Italian press. My Italian is much worse than my English so I'm having difficulties following this case in Italian. If someone is better at it, please do translate it for us, when you come across any new info