In his pinstriped suit, long coat and trainers, he looked so much younger than either of the earlier versions of himself that she’d known. It made her feel old by comparison, even though she knew that he was really hundreds of years older that she would ever be.
It didn’t seem fair that the older he got, the younger he looked on the outside while she… Well, time was leaving its mark on her, more so with every year that passed. There were lines on her face that hadn’t been there when she’d known the Doctor before, a few grey hairs here and there which she’d already resorted to hair dye to hide. What woman her age didn’t?
In her day-to-day life, with Luke and his friends, she still felt reasonably young. More mature and wiser than they were, that went without saying, age brought experience after all, but somehow they never made her feel her years.
But seeing the Doctor now, running around with his new companion, a slip of a girl, all blonde hair and white teeth, Sarah Jane suddenly felt… old. He’d moved on, found others to travel with him, lived who knew how long bouncing around through time and space while she’d taken the slow path through linear time. As glad as she was to see him, she was jealous; of him for looking younger instead of older, and of Rose for being young, so full of life and with everything still ahead of her, the universe and all of time just waiting for her to explore.
She wished that it could be her, that she could shed the years she’d gained, step aboard the TARDIS again and fly away to new adventures, but that part of her life was over years ago. Even if the Doctor was willing to take her travelling again, which she doubted, she couldn’t go; she had responsibilities here on earth. It was Rose’s time now, and as much as she envied the girl, Sarah Jane prayed that she would make the most of every moment so that in later life, she wouldn’t look back on her travels with the Doctor with regret, wondering what might have been. Because the day will inevitably come when just like Sarah Jane herself, Rose’s time aboard the TARDIS will end; she’ll have to go back to living an ordinary life, and the only things she’ll have left will be her memories of all the extraordinary things she’s seen and done.
Sarah Jane knows from personal experience, there’s nothing in all of time and space that hurts more than being left behind.