He tried for her and Harry, he really did. He many times convinced himself to not drink and to act joyful, for the sake of two of his favourite people.
"We talked about this, Padfoot, I have to go, for Harry... and for Pippa." She said and he sighed. "I know, I know." He mumbled. "Look after yourself, alright little Potter?" He asked and she chuckled. "I will, Siri."
He embraced her, kissing the top of her head and then watched her of as she herself proceeded to use floo-powder to get to Dumbledores office.
He welcomed her with a smile and she gave him a strained nod before heading to her classroom. She took the key out of her pocket and smiled when she walked into the room.
It wasn't really dirty, it just needed a rinse and she had to get rid of the dust, nothing a bit of magic couldn't handle. 
After cleaning, she looked at her class schedule and then rested a bit. After a while she headed to the great hall where she met with a few teachers, the students having not arrived yet.
"Ah, Diana! How great to see you back here." Sinistra greeted her. "Now I can finally have some night rest." She whispered to the woman making both of them laugh.
"It's great to see you to, Aurora. How are things? I've heard a few rumours about the new DADA teacher... is it actually that bad?" She asked and the woman nodded. "Don't get me started, she's horrible! You know, she's removed all the paintings in the castle! Not to forget she also almost fired Sybill! It was horrible." She said in whispers so no to many people could hear really.
"Speak of the devil." McGonagall butted in and the three looked up to find a toad like woman walk into the great hall like she owned the school. "I already hate her." Diana whispered to Sinistra. "I know right?"
"Miss Sardothien I presume?" The woman looked Diana up and down from where she was seated at the staff table. "Yes, you would be Dolores Umbrige? It's pleasure to meet you." Diana said with a fake smile, it really wasn't.
"As you might have guessed, I will be joining some of your classes to observe your teaching... see if you are- how to say it? Good enough." She said and Diana gave her a 'sweet' smile that did not quite reach her eyes.
"I will be looking forward to your visit." She lied and the pink woman gave a small, squeaky hum before walking off. The two Astronomy teachers exchanged glances and then rolled their eyes.
After a while, the great hall filled up with students who -mostly- gave her excited smiles and she gave the same energy back. Some waved, others elbowed their friends and pointed.
Dumbledore did a few words announcing some things that where new, and some things that were old, like the rules.
"Now, as some of you might have noticed, we have a not so new teacher in our midst. From today on, we welcome Professor Sardothien back into the faculty and she will continue her lessons like normal." He announced and many cheered and clapped, making first tears look rather surprised.
After the dinner, everyone went back to their common rooms and Diana went back to her own room.
When she arrived, she found an orange cat sitting in front of her door. "Why hello there, mister." She greeted with a smile and opened the door, allowing him to walk into the room.
There, he changed into his human form. She looked back at him and smiled as she put her wand on the table. He walked towards her and snaked his arms around her waist, burying his face into her neck mumbling something.
"What?" She asked chuckling. "I missed you." He said a bit louder making her huff a small laugh. "It's been a few hours, Reg." she said and he grumbled, making her roll her eyes.
Knock knock knock...
They turned to the door in shock and without hesitation Regulus turned back to a cat. "Come in!" Diana called and a girl walked in.
"Luna! It's after hours, what are you doing here?" She asked and the girl gave her a dreamy smile. "I wanted to see you." She said making Diana sigh.
Obviously she had been visiting Neville and Luna, though, it had been a while, she hadn't visited for Christmas, only sent gifts.
"You are in my class tomorrow, you could've waited." Diana said making the girl shrug. "I wanted to see both of you." She shrugged. Diana was taken aback and looked around for expecting to see someone that wasn't there.
"Hello, Regulus." Luna greeted and he turned back. "How did you know?" He asked and she gave him a dreamy smile. "The nargels told me, I've known since first year... I did keep your secret, though." She said, swaying on her feet a bit.
"Thank you, I guess?" He said a bit surprised. "Regulus, you know who she is, right?" Diana asked and he nodded. "Of course, you're Luna, you're Dora's daughter." He said with a hint of a smile.
"Is that all you know?" Diana asked him and he shrugged. "Is there more?" He gave her a questioning look and Diana bit her lip. "Luna is your goddaughter... Panda always believed you'd come back." She explained and Regulus eyes widened, before looking at the girl who smiled at him.
"I know it's a lot of information, but I just wanted to get to know you, the moment I saw Diana I knew she knew and that's why I came." She explained. "I just wanted to let you know, see you tomorrow, Diana." She then turned on her heel and left.
"Yes, that is Pandora's daughter, no hesitation." He said making Diana laugh. "That's your daughter number two, I promise that was it." She laughed making him smile.