I'm taking a little artistic license here. Bear with me as I try to make my point, silly as it is.
EXT. BAD WOLF BAY
The TARDIS dematerializes as Rose watches it fade away. 10.5 slips his hand into hers. They look at one another for a long moment. Then Rose releases him and walks slowly down the beach towards Mickey, who is standing alone, as he often does these days, with a sad look on his face.
Mickey: (concernedly) What just happened?
Rose: He's gone. Forever…
Mickey: Yeah, but what about him?
Both turn to look at 10.5, who is happily picking up small stones and throwing them into the surf.
Rose: I'm supposed to take care of him.
Mickey: (alarmed) What do you mean?
Rose: (sad look on her face) He's my responsibility. That's what The Doctor told me.
Mickey: But Rose! You had nothing to do with his creation. He's not your obligation. He's his… (looks towards where the TARDIS had just been)
Rose: (shaking her head, somewhat confused) But he needs me. I can help him. And he looks just like The Doctor and sounds like him and even smells like him…
Mickey: (even more alarmed) Huh?!
Rose: (sounding a bit dreamy) He's the same. He's The Doctor. He's got his memories, his thoughts, his feelings, his eyes, his body…
Mickey: (upset) Rose, listen to me. Remember… Remember when Ricky was killed? What if… what if you had still been in love with me then and it was me that got killed instead? Would you have taken Ricky? Would you have…?
Rose: It's not the same. Not the same at all. You were different, the two of you were different, and besides, I didn't love you, not like I love The Doctor.
Mickey: (pained look but pushing on) But, don't you see, it is the same. There's something weird about it. Something wrong. Were you even given a choice?
Rose: Well, no, not really…
Mickey: (looking at 10.5 who's still tossing stones) Was he?
Rose: (eyes flashing, defensive) No, but there weren't really any other options…
Mickey: Rose! Come on! You always have a choice! There's always an alternative! What were you thinking?
Rose: That he's better than nothing…
Mickey: (horribly sad) Yeah. Right. Nothing.
Rose: (looks down at her feet, ashamed but silent)
Mickey: (bitterly) You know, if this was a plot in a television show I'd say it'd just nuked the fridge.
Rose: (looks at him blankly)
Mickey: You know, jumped the shark?
Rose: (shakes her head) I don't get it.
Mickey: Yeah, that's right, you don't.
He turns and walks away leaving her standing alone on the beach, watching a man throwing stones into the surf.