I don't like it really but I tried. Sorry if this wasn't the invincible you wanted. I decided to go against the norm :)

Rose leaned over the TARDIS console as she looked at the Doctor, her Doctor, with worried eyes. They were running away from danger again but that’s not what bothered her. For the years that she had known him, he would always show his true feelings for her, but never act upon them. He was invincible an impregnable force that wouldn’t allow her closer than an arms length.

“Doctor,” She said quietly over the hum of the TARDIS. He quickly looked up her and beamed as she tried to hide the blush that always crept to her cheeks when he looked at her.

“Out of harms way,” He smiled letting go of the three levers he was holding down.

“Doctor,” She said again looking at him. “About what they said while they had us.”

“Don’t bother with that,” The Doctor said trying to wave it off. “There is
no reason to.”

“But I want to,” She said quickly. “You can’t be invincible to me for ever.
I’m not going anywhere.”

“I know,” He sighed looking away “I’m doing it for your own good.”