That is indeed the stated intent. The whole point of me taking lessons here is to learn positioning connectivity in the way you describe. So this is where we start.It’s a typo, no doubt. The only reason to write a D# in the key of Bb is to convey an ascending line (generally accidentals are sharp ascending and flat descending to convey direction of the line), but in this case I think it’s just an oversight. I really can’t imagine a teacher would try to trick a student, as there’s really nothing to be learned from it. If you were in a session or rehearsal and played as written, the BL is either going to stop you or shoot you a glare and have you fix it in post.
I would think the point of this assignment is to get you to see how walking bassists used chromatic connectivity in their lines, not whether or not you can spot a typo. Play it as mentioned, Bb-D-Eb-E, and if you want mention it afterwards. The real lesson here is chromaticism in walking bass. Happy learning!
I don't see it as a trick, though. I see it as an evaluation point. What can she see in this? Is she reading the flats and accidentals correctly? For a first lesson I don't see that as unreasonable evaluation. But I may be giving more credit than is due. I will find out. The big thing is that I'm not insane and this is indeed a weird way to write this.