From what I've read so far, I think u, ur bro and ur mom are doing fine. don't pressure yourselves too much.
Diff kids have diff personalities. they will figure it out eventually.
Oh, and bracelet kits and the make fake plastic food are a waste of money anyway.

i am a divorcee. me and my 2 kids live with my sisters so my son basically grew up in a 'lady's world'. like you, i was also very worried he may turn out ladylike but after 5 years, he still does guy things like playing guns, dinosaurs and going to robotics class. he's 10 now. he knows what a girl should(n't) do and what a boy should(n't) do. Also take it from me, someone who grew up with 3 sisters, there's no guarantee growing up with no brothers makes you more ladylike. I was quite a tomboy, grew up with short hair and all and I didn't like doing girly things so much. Still prefer wearing pants than skirts though i dont sit with my legs wide open. haha. again, just keep on reminding her to sit with her legs close. my 7 yo daughter still does it every now and then.

so long as you bring ur sister out mingling with other kids in the playground or mamak stall (what better place to see chinese, malays and indians together sitting, eating, chatting away happily without any prejudice), they won't discriminate ppl. In most cases, children learn to discriminate by watching their parents & other family members doing it. my son can barely speak BM so i deliberately bring my kids to mamak stall so they will learn to speak BM there and they can see that there's no problem mingling with other ppl other than our own race.

Honestly, my son does have problems making friends in school. He always tells me he's a loner in school but I figured it out that it wasn't because of his inability to speak fluent mandarin but because he just prefers to be alone. He doesn't have 'certain' friends or a gang. Kids will be kids, everyone is a friend to a certain extent.

Don't sweat it too much. Same situation as mine and I turn out fine. HAHHAHA.

And my friends used to be Malays/Bumiputras... It's only when I'm in high school that I have few Chinese friends.
None in uni, mostly acquaintances, but when start working, that's when I like really start interacting with Chinese ppl (other than family) everyday.

As long as she's not disliking her classmates because they're of different race. 

pros of that is that she sounds like she can handle herself independently and not gonna rely on men when she grows up.

If I may add in...she is still kinda young now...wait until the hormones kick in. And hey, not all girls like to play with girls' stuff i have seen a video online, a 10+ yrs old girl built her dad a freaking plane! So imagine that..dun wipe off her talent, instead understand what she likes and strengthen the interest of hers

pros of that is that she sounds like she can handle herself independently and not gonna rely on men when she grows up.

This!

Following from other comment b4 me, the girl might be naturally mimicking boys' lifestyle because surrounded by boys & no/less guidance from other females.

It IS a waste of money, being a scout lets you learn how to make practical cords and cook real food for free and those toys simply felt like a rip off. Especially when she doesn't even touch it. It's just sitting there collecting dust. And I thought it was only me who felt that girl toys are a waste of money. There's once when my uncle brought her to toys r us, and suggested buying her some sand castle kit, she said, "For what? You clean ah?" That made my day.

Thanks for sharing your experiences, it eased my mind. We live in a Malay neighbourhood with us being the only Chinese family, so she has no problems mingling with the Malay kids as they run about the streets during the evening sembangs or menyumpat group of which my mom is a proud member. Indians wise, my brother only has Indian friends, and whenever my drinking buddies come over, majority of them are Indians. Our Chinese friends and relatives either speaks English or Cantonese, so she has zero exposure to Mandarin speakers, which is probably the cause. Like your son, she complains a lot about not having friends and not being able to understand what the teacher says. But as you mentioned, kids will be kids, I'll just keep myself updated for now and probably give her a pet talk if it's really bad.
Yeah, I suppose you're right. As long as she doesn't turn out to be racist, it's better than any lesson she can be sent to.