Here's a glossary link for you:
LGBTQ Glossary | LGBTQ Life
From what I understand, she's a non-binary asexual who is trying to cheat the covid system by pretending to be a family member (lesbian partner) so she can eat at a restaurant. It's silly but maybe she's been cooped up with her mom for too long during this pandemic, this is her way of getting out. She's having her fun by playing the system. I honestly don't think there's anything more than that.
One can be non-binary AND asexual or bisexual or gay or straight. Non-binary just means a person does not identify as a man or woman. You mentioned she's masculine? I think that's a common feature for a non-binary woman to look masculine.
Being asexual does not mean a person does not talk about or engages in sex. As yourself for example, you identify as an asexual but engage for the purpose to please your husband.
She may have once been interested in you, in a non-binary and asexual way.
Being bi or gay does not make a woman masculine. There are many types of lesbians and bisexuals, some of which are very feminine. So, the fact that she's masculine looking does not indicate she's gay or a lesbian.
Being non-binary and asexual is part of the LGBT2QIA Community. You can also be heterosexual and be supportive of gay rights.
Why isn't she being honest? Maybe she is and you're not understanding it. Or, as you've said, there are barriers in her life that may prevent her from coming forward.
She's jealous that you're married and she's not? Being non-binary and asexual is a sexual orientation and not a choice. Sometimes people are upset when they discover their true orientation because of the stigma, prejudice, and limitations it comes with. I'm sure it's a common phase of grieving to wish to be heterosexual and married with a white picket fence, a child, and a dog. Life just doesn't always work out that way.. and hopefully, after their grieving process, they'll come to acceptance and lead a happy and fulfilling life as their true self.
Yes, one can be pretty and beautiful and be overweight.