Also they need approved visa and written authorization to travel too. Given your wife is having a baby mid March, your sister would need a place to quarantine for 14 days. Can you provide separate bathroom and bedroom? Will you bring her meals to her room? She is not allowed to venture out. You would not want your sister around a baby.
All you can do is apply. Many people want expedited processing and your sister is not immediate but extended family. Start with the visitor visa. Your sister has to show strong ties to country and she needs to show she can afford to come.
The room must be in a separate location in your home. Pregnant women are at high risk of covid complications and considered vulnerable and infants are fragile when it comes to any infection. Pregnant women and infants have contact with the healthcare system so they must not be close by to people who are quarantining especially since we know the virus is aerosolized and remains in the air for hours. "Helping" your wife can be considered work if doing things like cooking and cleaning.
