Does switching majors look bad for graduate admissions?

Changing majors is actually more or less a good thing when it comes to graduate. It's actually more common than you think, with some people changing major in the middle of their undergrad career, between undergraduate and graduate, or even maybe during graduate studies itself. It's a sign that you know what you like and you don't like, which is a good thing when you eventually apply for graduate school. And if you know what you want to study for graduate school, you might as well get a head start while you still can, and it will also be a good thing to explain if graduate schools question your lower grades in ChemE, especially if you experience more success as a BME major.

The only issues that this will present here, is how much of the undergraduate curriculum for BME you would be able to cover, as you noted you would be a junior when transferring in. Is there any of the chemical engineering coursework that would transfer to satisfy requirements for the BME major? Since you have two years left, assuming you want to graduate within the four years, would you be able to satisfy all the BME degree requirements, as well as gain research experience or an interest into a specific subfield (through electives) by the time you graduate? You may find yourself needing to take a extra semester or two in order to finish the requirements of your new major.

TLDR: If you feel you would be happier in the new major, and you can do so with more success, I would go for it and change to the BME major. Hope this helps.

TLDR: You should switch majors

Engineering (of any kind) is hard. If you are excited about it and love it, then putting in the work is possible. But if you hate the classes, you are going to find it very hard to be motivated enough to do the work needed to get As.

And you do want As for grad school. One bad semester won't kill your grad school chances. Four more bad semesters in a row will.

Either Electrical or Mechanical are both good starting points for BME (just as good as if not better than Chemical). Pick whichever you suits you best and switch.

Changing majors isn't likely to be a factor in itself. When creating a CV or resumé, you can choose what to put in and omit. Ultimately you will want to shine a spotlight on a particular qualification as the proof that you meet the criteria for the particular job (or course in this case). To this end the particular major you have pursued, followed by the grade you achieve, are the most important factors. If you change major you can simply leave out the previous course your pursued.

In my experience a 1.1 or 2.1 or even 2.2 degree in a relevant subject is plenty qualification for a masters (perhaps not a 2.2 for research masters). That's what... about > 3.08 GPA. I'm not privy to your specific circumstances, either in terms of the university you are going to, or the particular course you are attending, but demanding an exceptionally high GPA to qualify for a masters seems unusual to me (unless there's some sort of scholarship element)

The issues with changing course stem from monetary concerns and those relating to motivation. Going back to scratch in terms of most of your degree is a big ask, and you would be wise to work out in advance if it's something you will be prepared for, both mentally and financially. A degree with an average GPA is infinitely better than a hypothetical degree with an excellent GPA that never gets finished. On the flip side if you don't think it's likely that you will be able to finish the current major you are doing (either because you find it too difficult or just not enjoyable enough) then you have nothing to lose by switching.