Just ignore them and keep doing what you're doing. They don't know what they're talking about. She'll have no problem picking up English if you live in the U.S.
She's only 13 months old. Two of mine didn't say anything at that young age.
I know it's tough to ignore criticism. The easiest thing to do is to NOT explain things. Ignorant people wont easily be educated. Only time will teach them. I had my mother-in-law, herself raised bilingually, telling me that I was "confusing" my son by speaking English to him. Then a few months later she brags about her grandson being bilingual... I couldn't win!
Often, I'll simply call their bluff. Actually tell them "Careful! She might not understand you. She doesn't understand English yet". Then it's hard to lecture you if you've already "admitted" your "guilt".
I also did a lot of "WHO told you THAT!" and then I'd mumble about "people" who don't know squat about raising children bilingually/breastfeeding/scheduling, etc. I'll even try to draw the speaker into the criticism. "Can you believe people actually believe...??" I got it more for breastfeeding than the bilingual issue. I would also make dismissive statements. "Oh bottlefeeding is so much work. Too bad your breastfeeding didn't work out..."
An example in this case would be to simply smile and say "We're certainly not worried about her learning English living here in the U.S. It's the X we need to concentrate on, to make sure she is fluent..." When you make proclaimations like this, it's really hard for someone to come in and deconstruct them. Don't be afraid to REPEAT what you just said. You can even emphasize it with statements like "As I just said, since we live in the States, she'll get plenty of English..."
I would even play it to the hilt. I would point out things like "She already says X, Y and Z and she's only 13 months old!" Then they'd have to play kill-joy and add that it's not in English...
Problem is that there will be people criticize you for everything when it comes to parenting. If the issue is safety or health related, it's worth listening to say, car seat advice. But bilingual or say, sleeping issues are not in that category.
The fact that you're Asian-American might have some psychological issues wrapped around their criticism. They may be desperate for your dd to fit into American society. They might be misinformed about accents, especially if some of the relatives have accents themselves. You may not want to address this, as they may not even know that's their "fear".
Acknowedge their concerns. "She'll hear English in the park and after all, other children are the BEST language teachers!" or "Our babysitter says she manages... and she's understanding a few things in English..." just to let them know that you're not entirely ignoring her English learning.
Don't be afraid to stick up for yourselves. These people are very misinformed. My mom's boss, a bilingual child himself, asked me why I "forced" my son to speak both languages from the get-go. Don't you want to wait till age 2 before making him do this? Of course, I didn't want to offend my mom's boss lol! I realized he was more concerned with the "burden" I was placing on my son. I told him "Yes, my son is delayed speaking but it doesn't seem to bother him too much. He gets his point across..." Now today, my children are trilingual and his grandchildren are monolingual. I no longer hear about any "burdens" they have to bear. I'm still really fond of him and I resist all temptation to say "I told you so". He's legitmitely sad that none of his grandkids speak his language (or his own children, very well).
I will add that support actually can be what you regret wishing for. My mom runs around lecturing non-native English speakers to use their language and ONLY their native language with their children. These are the boss's clients! She endlessly prattles on about her "perfectly bilingual grandchildren who also speak a third language". A guy came over to tile the bathroom who was originally from Peru and he got the Whole Speech. She brags about how many parents she's convinced to raise their children bilingually. "You're going to be glad you did!"
It's nice to have a SUPPORTIVE parent but in her case, it's a bit too much of a good thing. So I'm suffering the opposite than you are. We can't win either way so don't even try!