The 32-year-old singer- who has been dating the 25-year-old Formula One driver since 2007 - admitted while she dreams of getting married and being the typical strict mother, she is still focusing on her career at present.
She said: "Do I see us getting married and having children? My head says yeah, but I'm really focused on my music now and I think that will come in time.
"I think I'll be really strict like my momma, maybe even worse. I won't let my children out of the house! I'll make them listen to classical music."
However, if Nicole and Lewis do end up tying the knot, it is unlikely the brunette beauty will be going on a strict diet, as she has relaxed her healthy eating regime since her days in the Pussycat Dolls.
The 'Poison' singer added to You magazine: "I'm a perfectionist, but I have been trying to be a little easier on myself. I love my pasta, my chocolate. I love making down-home Southern cooking and having cakes and pies and baking stuff.
"I'm taking a break now. For a couple of years, at the end of the Dolls, fitness was my life. I'm a lot more relaxed now."