Words have meaning, but legal truth and reality truth/life truth/emotional truth are not always the same thing. For example, religious people can be married by a religious leader, and still not be legally married, and consider themselves husband and wife, and under the law/contracts of their religion, they are married, though legally they may not be.
I will share my situation/story in the hopes it gives you some comfort. DH and I were not legally married. We were legally domestic partners. Within the first month together, though, he started calling me his wife. Within a couple months, we'd exchanged "wedding" bands, and I changed my name legally. Everyone called us husband and wife. We called each other husband and wife, for years. We always planned to "make it official," but it made no difference in our lives. It did make quite a difference in death, though.
I continue to call him my husband. Though not technically correct, it's what we called each other in life, and I will NOT demote him in death. Also, convenience. I don't want to explain to every random person who somehow comes to know part of my story all that I just outlined above. It means more to me than to them, and I don't consider it a lie, though it's technically untrue to say "widow." It's kinda like this to me: I don't eat meat. I haven't since I was 12. For no real reason, I just don't. I do, however, eat fish now, but no shellfish. When I'm talking to acquaintances who, for example, I happen to be having lunch with, it's expedient to simply say I'm a vegetarian. Why on earth do I need to explain all the little aspects of my eating habits? It's technically a lie, but who cares?
One of my widow friends, in the early days, told me a story about how her sister kept (cruelly) bringing up over and over how she wasn't a widow because they were only engaged and not married. I had a few choice words which I will not repeat here. YOU know you aren't *legally* a widow - why must she point it out? It's easier to say widow than to say I lost my fiance every time you need to explain it.
And emotionally, inside yourself, which - let's face it - is where we live: it's true. F everyone who wants to hold you to technicalities (like, really - you just lost your future and your person - who gives a shit about legal status?!). And yeah, words mean specific things, but we don't have a word for this, and widow is the closest one. Only @$$holes will call you on it (sorry for name-calling your mom, I'm sure she's wonderful).
{Edited to add: When a person asks me how long we were married, then I divulge the whole technical truth, and explain why I use the word widow.}