Or she married a gay man and she believes gay sex is a sin so stayed a virgin. She married to be a mom because married different sex couples get placed with kids easier than single ones.
Okay--so here's my theory. She married a friend because she felt she had to get married. He knows she is a lesbian, they have been friends for some time. She loves him, just, platonically. She is a virgin--just the case. Her children are adopted. She is on tinder looking for a girl to hookup with. Obviously her attempts so far have been fruitless.
If she adopted kids, and is actually bisexual, in a polyamorus relationship, and jokes that she's a lesbian.