I don't think it's the costume, she genuinely loves Bruce.

She loves Bruce. Refer to my avatar for further confirmation of how much you do not want to debate that with me.

well he's proved that he has a thing for milfs so why not

" @FadeToBlackBolt: Please, my  blog, I'll debate whoever I WANT. Check out Gotham Sirens #7 for proof that there's some heat going on between Dick and Selena. And besides, love doesn't necessarily stop a woman from getting some, especially if the object of her love is dead. Think Richard III and Lady Anne, or Lois and that pony-tailed dude, the photographer, right after Superman died. "

" @FadeToBlackBolt: THAT would be cool! And hey Dick is a player, like father like son, you know? So yeah, I think Dick would play with the pussy (cat) if she gave him a little whiff. But maybe he wouldn't, to honor Bruce. I dunno'. "

It wouldn't bother me seeing Diana with Bruce. It's a nice alternative. 

idk where you guys are getting any of this from.
 Selina doesnt flirt with people because shes a tramp. She, just like Ivy, uses seduction as a distraction. 
And shes been NOTHING BUT loyal to Bruce. Almost everything shes done in the last 3 years was for him. Salvation Run, where she was his spy at great risk to herself. And If you've been reading Gotham City Sirens, she had to go through hell to keep his secret from Ivy and Harley, her only only other real friends. Shes a theif at heart, but now all her thievery is against criminals in a Bruce-approved manner.
 and on the other hand, Dick has 2 women around his age hes actually in love with, and like 3 others he still has feelings for. He has never been a "its there, so i'll go for it" kind of guy. Even if he was kindof attracted to Selina, shes like 10 years older than him and in love with his father-figure.
 If Bruce was dead for 5 years, Grodon and Starfire died, and he somehow lost someone like Damian/Tim/Alfred, then maybe they would fall into it. 
 But as it stands, Selina is truly loyal to Bruce and remembers when Dick was 12 in the robin outfit, and Dick has a bunch of unresolved relationships, and has yet to show any interest in anyone more than 4 years younger/older than him. 
No. I do not think Selina and Dick could/should hook up.

" idk where you guys are getting any of this from.  Selina doesnt flirt with people because shes a tramp. She, just like Ivy, uses seduction as a distraction.  And shes been NOTHING BUT loyal to Bruce. Almost everything shes done in the last 3 years was for him. Salvation Run, where she was his spy at great risk to herself. And If you've been reading Gotham City Sirens, she had to go through hell to keep his secret from Ivy and Harley, her only only other real friends. Shes a theif at heart, but now all her thievery is against criminals in a Bruce-approved manner. and on the other hand, Dick has 2 women around his age hes actually in love with, and like 3 others he still has feelings for. He has never been a "its there, so i'll go for it" kind of guy. Even if he was kindof attracted to Selina, shes like 10 years older than him and in love with his father-figure.  If Bruce was dead for 5 years, Grodon and Starfire died, and he somehow lost someone like Damian/Tim/Alfred, then maybe they would fall into it.   But as it stands, Selina is truly loyal to Bruce and remembers when Dick was 12 in the robin outfit, and Dick has a bunch of unresolved relationships, and has yet to show any interest in anyone more than 4 years younger/older than him.  No. I do not think Selina and Dick could/should hook up. "

Selina already had a brief fling with Dick when he was Nightwing...

As long as he doesnt act like this

No. I don't want to see Bruce and Dick against each other on the Maury Show.