Susan didn't exactly remember when the tables switched when it came to her and her grandfather. She remembered being younger and giving thing that sounded like orders--which was an automatic scolding for not being polite. And all the sudden, he's giving her orders! To her benefit when she demanded something, she never told him "fetch!" as a little girl. Susan remembered pushing her limits with him as all children do to their guardian, but Susan remembered knowing where and when she should push those limits (or else she'd probably get a pop on the mouth).
But he offered sundaes and since Fred was going, so would she. There were moments when she really, really hated her luck for having such a emotionally retarded incarnation as her Doctor. But then he'd say something rather endearing, and Susan forgave him. She practiced what she preached; she turned the other cheek.
That didn't mean she didn't let go of Fred's hand. She always held her hand. Bystander's said it was cute and Susan only wanted to ensure that her cuteness never faded. She liked being cute. She knew she was cute. Heck, she knew she was all that and a bag of chips! So she walked into Torchwood with pink trainers and silver lace, black tee with the Spiderman logo, and golden hair put into a french braid.
Susan really hadn't been eating much, sleeping much, or...well--that's about it. Two necessities that even Time Lord's/Lady's needed and she wasn't really doing it. Everyone handled stress in their own way. With Susan, she handled it by sporadically avoiding the stress--the rift, going back to being homeless--with something else. In Susan's case? Starvation and sleep depravation all for the sake of spending her time, when Dalton and Fred were asleep, at a arcade with a DDR machine (she knew in her hearts she'll gain a higher score than 'xxPrettyBoi44'!)
So when her stomach gave a growl at the thought of food, even if it was ice cream? It did the thinking for her and Susan was glad to be lead toward the kitchen area to sate said growling.