Your girlfriend wants to spice things up - she wants to show how she excites herself and makes herself cum. As you watched her, she'd invite you to pleasure yourself, too. She shows off her pink lingerie while stripping out of it, then squeezes her big tits and pinches and pulls her nipples. She bends over to expose her tight holes. She masturbates using her fingers, then brings out a vibrator and dildo. She presses the vibrator against her clit in multiple positions, then fucks herself with the dildo. The two of you would orgasm together. Maybe she'd get some new toys and you could watch her do it again.