Tha sounds fine, she could just be more focused because it's nighttime and there are no distractions! Usually when babies have a nursing to sleep prop, they wake up frequently and only take enough to get back to sleep -- when they're littler, a lot of babies still need to eat a few times a night -- eventually she may need some help stretching out the feeds at night, but it's also possible she'll do it on her own.
Forgot to ask earlier - how old is she?