You will get different answers from different sources on this one as it is a cultural issue.
In some cultures (ours), sleep training is the norm and babies are trained to sleep thru the night at very young ages and co-sleeping is discouraged as the goal is for the baby to associate objects with sleep, not people (ie: crib, blanket, pacifier). If you subscribe to this philosophy then yes, you are allowing "bad sleeping habits" nuring naptime, which are being transferred into the night. BTW, co-sleeping on a couch is dangerous, you can only do this on a flat mattress.
In other cultures, it is recognized that babies were not intended to sleep thru the night consistently until they are 3-4, and night waking is completely normal. It is also assumed that a baby sleeps next to mother, as this is best for both (reduced possibility of SIDS, better temperature regulation of infant, more opportunity to night nurse, and for the mother more sleep, more opportunity to night nurse providing natural birth control when baby is young and also lowering of estrogen levels/raising of prolactin and oxytocin levels thus reducing risks for certain cancers). If you subscribe to this philosophy, then what is happening is that your baby has gotten a taste of doing what comes naturally at naptime and is showing her preference to continue this at night.
The only person I know of who devoted a career to researching breastfeeding, sleeping thru the night and cultural influences on both is retired researcher Kathryn Dettwyler a former PhD Anthropologist at Texas A & M University. You may want to check out her website: http://www.kathydettwyler.org/dettwyler.html