When you're going to dildo fuck her, try getting her to dress in her sexiest gift wrapping so she's feeling hot and horny to start with. Blindfold her and use some roleplay while you're eating her pussy, she will love it if you fuck her sweet little married pussy for her. Talk to her while you're doing this, telling her things like how beautiful she looks, how you love her gift wrapping, how hot it is that she lets you fuck her with the dildo, how good it is to see her pussy wrapped around a big cock for a change, how you love seeing her cum so hard, ask her if this big cock feels better inside her pussy sometimes. Ask her if she thought she could take a cock that big before now (depending on her answer) ask her what was the biggest she's had before, make sure you're eating her pussy, kissing her mouth, sucking her titties the whole time, may be refer to the dildo just once as her friend's big cock (depending on her reaction to that question you'll be the best judge on how far to push the roleplay and the previous lover questions) neve push for answer, instead just move on. Remember this is all about her pleasure, not yours.