Husband's step mom wants to come over

I just had a baby 3 weeks ago. My husband's birthday is Thursday and his step mom wants to stop by to see him. They're usually up in Canada but are visiting down here in California for a few weeks. I honestly don't want her to come over. She doesn't want to see me or even her grandchild. Just my husband. She legally adopted my husband when he was 14. She doesn't really like babies. She came into my husband's life when he was 10. So she wouldn't be here to see me or give us a break from the baby... Just to say hi to my husband. She's never made an effort to get to know me. My husband tells me not to mind her because she's autistic and got diagnosed way later in life. So I try not to let things bother me. I understand it will be my husband's birthday but I JUST had his baby. It already feels like I'm chop liver because everyone cares about the baby and nobody cares about me. My husband's step mom cares about neither and will have no interest in our baby until they're no longer a baby.