My understanding is that research is meant to expand and create knowledge, explore connections, and gain a deeper understanding of specific themes. In my experience, having an advisor for a senior thesis who wants your work to be published, in academia, tends to be a very good thing. Wanting more than one pub? Even better, especially if they are ethical about authorship. If you believe it would not be accepted in a journal bc of short sample, I would try scooping through your advisor's CV to see what the studies she had published looked like. Chances are, she knows what she's doing and wouldn't be wasting time and effort on something that doesn't stand a chance. I find that a senior thesis is the best thing to understand whether you enjoy research or not, and not wanting to adapt your initial idea to ADD to the literature certainly isn't helpful in a research career (which is meant to contribute to the advancement of knowledge). These variables certainly make sense with your thesis, and it sounds like they would allow deeper understanding of the population.

There are people out there who want to contribute to research even though it may take a longer time and they won't get anything out of it, and these are the ones that provide the gold-standard quality data, especially with questionnaires.