Divorced fiancé parents, what to do with rehearsal dinner and reception?

My fiancé’s parents get along very well . They have been divorced for 20 plus years. The issue here is that his mom thinks it’s mean that she walks down the isle with her ex husband instead of her boyfriend she’s been with 14 years. He has been there for her medical issues and cooks a lot for the family. What should i do? I didn’t have her down with him to walk in as the bridal party at the reception but with her ex husband thinking that would make sense.. She wants to walk in with him at the reception in the bridal party plus also walk down the isle at church, this possibly leaves my fiancé’s dad to be alone... do you think this is wrong? She is insisting to pay for
rehearsal dinner even thou we are trying to pay for it. My mom is deceased and my dad is visiting from South America , so i was thinking to have them both together but she didn’t want that. I think i May have cross the line? She is also putting down 1,000$ for our wedding with my fiancé’s dad another 1,000$ and she got us lots of gifts for bridal shower... what’s the right proper way? Should she walk down with her boyfriend of 14 years? Please help ! Our wedding is this coming up Saturday. I am stressing .