Not true. I know several older sisters who became sisters later in life. One of them even had grandchildren when she entered her community.
It’s ultimately up to the individual order, or even each monastery within the order. This applies to both men and women alike. It’s not common you’ll find someone accepted into any community as a “senior citizen”, male or female, for a number of reasons, but it does happen on occasion. However “late vocations” are not uncommon at all, male or female. The upper age limits you often hear about are generally just guidelines, some communities stick to that guideline more strictly than others. Superiors can make exceptions as they see fit. Sometimes the exception needs to go up the chain of command, but if an older person truly has a religious vocation, the Lord will see to it that age does not keep that person from fulfilling his or her call.
