N.S.
I think it's perfectly common to have a stepkid get all over their bio parent and be jealous of the other kids in the family. My SD is 9 and she will crawl all over daddy and make him carry her around the house and want to exclusively have his attention. I have found the best thing to do in those situations is to let the child do it, she is obviously feeling needy. If she's pulling her daddy's face toward herself and away from the 23 month old, then your husband needs to reassure her that he loves her. I would suggest some one-on-one time with just daddy and her, perhaps you watch your 23 month old and let daddy take her out? My SD does much better when she gets some one-on-one time with daddy, even if it's just playing a game alone together for 30 minutes. I usually take that time to relax with a cup of tea and a book! I enjoy my "me time" and they enjoy some daddy-daughter time. If she's still like that AFTER daddy-daughter time then she needs an explanation from daddy that he's her half-brother's daddy too, and he loves them equally, and it's not okay to act that way.
Step families are a strange dynamic. The more you can roll with it, the easier it is.
My SD does the same things your SD does, and she's 9! Just keep after her (after all, it's YOUR house even if you aren't her mother) and let her know with patience that her behavior is not acceptable. She might need help cleaning her room, or she might need an incentive. You don't know what it's like at her mom's and your rules are different. So she might need extra help knowing what to do, and an extra reward afterward.
Keep up the great work! Being a stepmom isn't easy, but it has its own rewards! It's hard for anyone who is NOT a stepmom to even imagine what it's like. As for your husband calling you jealous, I don't know if jealous is the right word, it's just a different dynamic. In traditional families you have your own kids and they belong to both of you. In a step family you have someone else's kid that is NOT yours, and your husband to a certain degree, is still connected to and trying to raise a family with his ex. I have noticed that when my husband has accused me of being "jealous" he was in fact, shutting me out on purpose for fear of losing his special relationship with his child. I felt that shutout and was hurt. One time he took her out to see a movie that I had been excited about seeing with him. He didn't tell me they were going, and when I was upset he accused me of being jealous. Of course I was! Later on he admitted that he felt he was losing his special relationship with her and had taken her to the movie on purpose! Now we communicate and of course they have their daddy-daughter excursions but because we communicate I have no feelings of jealousy, just gladness that they have this special bond and I enjoy time to shop with my girlfriends! Communication is KEY!