As the opening hymn ended and we all sat cross-legged on the chapel carpet, Mary Kate was practically trembling with excitement. When Father Dan asked us to bow our heads and pray silently, she held up her hymnal for cover and, eyes sparkling, asked me: ‘Hey, do you think I should take a selfie stick?’

‘Do I look okay?’ Mary Kate asked for the thousandth time.

It was Friday night, the night of her lake walk with Caleb, and she was finally ready. It had taken us two hours to prepare her; we’d even missed Fajita Friday for it. First, I’d talked her out of taking a selfie stick by reminding her you needed two hands to use it, which had convinced her right away. There was no way she was letting go of Caleb’s hand. No way. They were getting all the way around that lake.

Then picking out her outfit took at least forty-five minutes, which is a ridiculous amount of time considering almost our entire joint wardrobe consists of school uniforms, gym clothes and a cowboy hat, a feather boa and a Yoda mask left over from Halloween last year.

Clearly, she went with the Yoda mask.

Just kidding. Although that would have been amazing.

She stood on Girls’ Quad in her pink cardigan and navy dress with pockets, plus my fox-print tights for a touch of whimsy. Her hair was loose and she was practically bouncing with excitement.

‘You look perfect,’ I reassured her. ‘Go with God. Almost literally.’

She squeaked, twirled and skipped across Girls’ Quad, where the September sunset revealed the tips of the trees turning gold. Watching her go, I felt suddenly sentimental. My little Mary Kate, all grown up. In my head, I still pictured her as the tiny, terrified fourteen-year-old with big brown eyes I’d met during that deadly freshman dodgeball game. I had always felt like a big sister to her, even though we’re the same age.

And, actually, I was kind of a big sister to the whole dorm, as I was reminded as soon as I walked back into St Theresa Hall.

‘Alex!’ came an urgent hiss from the stairwell.

I went and looked up. ‘Preeti?’

Preeti I actually know, unlike a lot of the younger girls who come to me for help. She was my freshman buddy this year. She pulled me up the stairs into her dorm room. The dresser doors were flung open and her clothes were all over the floor. ‘My room-mate found my weed!’ she cried.

I put my hands on her shoulders. ‘Okay, calm down.’

‘It was in here – a little bag – it was definitely in here. Now it’s gone. My room-mate must have found it!’

‘Who’s your room-mate? Is she cool?’

‘Annie! Annie Rubio! The choirgirl! The one who’s super into the tambourine!’

‘Tambourine Spanker is your room-mate?’ I said. ‘Oh man, she is not cool at all.’