Also please tell your sister to stay busy. Go out and have fun. Spend time with the family & friends she lost contact with whist she was busy Dipsticking.
She might start to reminesce (sp) about the good times, the good things about Dipstick's personality. And as far as my two cents about knightinshiningarmor? Please please PLEASE tell her to NOT get involved so quickly after being with a losery wimpy Dipstick!!! She's EXTREMELY vulnerable right now and even the Devil himself might look inviting and innocent next to what she just left.
She needs to be ALONE. No dating. No running off to another man. She needs time for HERSELF. If she's a social butterfly, she can surround herself with friends... they're only a phone call away. Tell her to DESTROY all the photographs of this guy; destroy all tangible momentos. Destroy everything. No going back. Period!
And, as far as memories, I know you cannot destroy those. They are actually going to come in very handy. She needs to (RIGHT NOW) write down --- black & white --- all the BAD THINGS he did, said, and especially -- - write it down how he MADE HER FEEL. Go back and read it --- re-read it --- til she's got every letter memorized. Only THEN, once she's got it ingrained in her head she's done the right thing (As she may doubt herself for a while, and be tempted to fall back into the old familiar shoes) --- she can PURGE the memories. Get rid of him entirely, even in her head, and more importantly; her heart.
Abuse can break your mind... your heart... but it cannot break your spirit. If anything, after she's gone through all the stages of healing, purging, and gaining her self-esteem back -- she will be much, much stronger. Some day, she might even thank him.