It happens. And some siblings are jealous of each other for various reasons all their lives. The reality is that you can't make them drop those feelings. And you can't build the ideal relationship you want them to have. They are young, but the reality is that the relationship they eventually have will be the relationship they build or do not build. It won't be because Mom or Dad built it for them.
You can, however, have control over your relationship with each child. It sounds to me like your daughter is very clearly telling you that she feels left out of the attention circle. She's only 5, so she can't reason like an adult, but when she she says you love her sibling more, you can ask if she thinks that because of . . . whatever she just saw happen . . . . (you laughed at the little one, or read her a book or something) She'll let you know if that's right, and you can remind her that you read books with her, too, and that you laugh when she does something funny. If you have a photo album, you can also show her pictures of herself at that age, and talk about what she did, and things you used to do together. That way you are building a stack of "memories" (which she doesn't really remember yet), that she can take out. She'll be able to know that you did things with her, and that when her little sister gets big like her, you will end up doing the kinds of things you now do with her, while she will have grown up and will be able to do better things, and there will be so much more you can do together, because she will be getting older and bigger and more capable. And always, be ready with a hug and an I love you. She may just need reassurance. And if she gets the reassurance she needs, in a positive way, the negative behavior will recede.
On the other hand, 2 year olds have a great ability to move around and get into their older siblings toys and stuff. So they WILL DEFINATELY butt heads over that. That isn't a jealousy issue, that's territorial. And you may need to talk with the bigger sister to find out what toys are special and are to be reserved away from the younger one. They could go on a higher shelf, or in a special place where the little one can't destroy them. The other toys that she's willing to share could be in a "public" place. Then she has to learn that when she takes a toy that isn't hers, the 2 yr old has the right to ask for it back. It goes both ways.
The thing to remember, too, is that the older one will be going to school soon and broadening her social circle, and you will be able to share school pictures and homework and all kinds of things the little one doesn't do yet. So there will some very special days ahead for you and her, and those may make a big impression on her. It may make life easier, and it may not. But it will certainly give you times when you can praise her, welcome her home from school, and make her feel very very special.
Parenting is a big challenge. You just want so much for your kids to grow up happy and to love and befriend each other. Our younger 2 are great at that. Our older two (adults now) still have issues with each other, due largely to the manipulative behavior and periodic partiality shown to them by my ex and his family. It made life very hard and increased the jealousies. This past week the younger one called to tell me they'd had a big fight over the phone, and she and I talked. I was burdened for them all night, and I considered callig, but didn't. I considered e-mailing, but didn't. I had to sit on my hands and heart to stay out of it. And I got a call the next day that said, "We talked again, and we cried and we patched it up. Everything is okay now." If I had gotten involved, it probably would still be a mess, but they are working through their issues and they care about each other enough not to let the other go, even when they are angry. .. . . It takes time. . . . and maturity . . . . but don't jump ahead and worry about what happens 20 years from now. Listen to the needs the kids express to you, and try to meet those needs on the 5 or the 2 yr old level they are at today. Meet the needs as appropriately as you can, and keep growing with them. There will be times when they are happy and times when they are grouchy, but what you are building are relationships that will say, "You belong to me when you are happy and when you are sad" and you belong to each other then, too. It'll all work out .. . .but you have to wait 20 years sometimes to see it !! :-)