I guess my perception is that if you need monogamy and your partner needs polyamory, you are not a good fit ... if you sacrifice and try poly for her, you are already engaging in the kinds of self-sacrifices and lack of boundaries that set up ENM relationships to fail, imo ...
it sounds like the only reason you are trying poly is because you don't want to lose her, and you feel it's better to keep some kind of relationship over having no relationship ... which I understand (hell, when my girlfriend cheated on me I was "ok" with it because I didn't want to lose her, but then she dumped me later anyway); but I will point out, if you are sacrificing on something as important to you as mutual commitment out of desperation, then you aren't in an equal and healthy relationship at that point
so my advice would be to work on your self-esteem and learn to recognize and protect your needs - recognizing needs and setting boundaries is legitimately hard, and self-esteem issues are not uncommon for trans individuals - just know you're not alone in these struggles ๐ซ