As per CRS scores mentioned by you that is 459, Your Fiance should make an express entry profile. The current CRS score cut off for Canadian Experience Class was 454. There will be next draw in coming days which can be around 454-460. If she has an active express entry profile, she can have chance to receive an Invitation to Apply.
1. Yes. We can help her for Canadian Experience Class application.
2. If her mother already has a valid visitor visa for Canada. She needs to have a written authorization for travelling to Canada by IRCC. This is totally based on the purpose of visit. You can plan your wedding in April 2021 and call her mother to be a part of it as an immediate family member. You can still go for the civil marriage first and religious marriage later on if there is an issue of status in Canada for Arshpreet. Otherwise, Arshpreet can still go for her own application under CEC class. If you have further questions, feel free to ask.