i don't understand why my aunt feels the need to lie to me

Last year we signed our license and this year we're having the ceremony and reception since we paid for everything already 2 years ago and can't move the date again. Unfortunately, my great uncle passed away unexpectedly last week and his funeral is this week. Our wedding is the 27th of this month. With the dates so close together I knew some of my family would have to choose between attending the funeral or the wedding. My husband and I contacted my family members this last Saturday to check how many people needed to change plans so we could update our count for the vendors. We made sure to let people know that we understood thier choices and were okay if the funeral took precedence for them. Most people were fine we had to adjust numbers a bit. However, when I talked with aunt, she kept trying to make excuses for why she could only do one event. We kept telling her it didn't matter we just needed to know if she was coming or not but she kept coming up with excuses. It wouldn't have bothered me so much if her excuses hadn't all been lies. Her first story was that she didn't have the time off available to do both. But I had just talked to my grandma the day before and my aunt had told her she was planning to come to the funeral then go home then come back the week of the wedding to help my grandma sort my uncles' estate. Then she said she said she needed to go to the funeral because my 16yr old cousin begged her to go, that it was super important for her to be there. Except my cousin posted on her Facebook that her mom was forcing her to go and she was upset she was missing practice. I figured it was some kind of grief thing and didn't call her out on it, just assured her it was fine and hung up. Then today she messages me again with more excuses! The on that got me the most was her telling me my older cousin wouldn't be able to make it because she's struggling with her medical bills from when she had covid. That would be fine if I hadn't been messaging my cousin all weekend. She had planned to come to the wedding she had a hotel room booked and her car serviced and she was going to drive down with her kids, leaving her husband and home to care for thier pitbulls. She then told me she had to cancel those plans because her mom begged her to dog sit for her. My aunt has two dog-aggressive and poorly trained corgis and she told my cousin she couldn't afford a dog sitter so she needed her to stay home to care for them. My cousin's husband can't work and watch 2 houses with dogs alone and they can't be in the same house because of the corgis' behavior. My cousin was telling me how she offered to pay for a dog sitter but my aunt quoted her some insane price so she eventually agreed to stay home.