Am I The Asshole For Ruining My Daughter's Winter Break Birthday Sleepover

My daughter's birthday(11th) is super close to Christmas so every year I let her have a sleepover. She invited 3 friends. Her best friend in 5th grade this year is a girl name Olivia and she's a sweetheart. Her mom is just protective. She's not allowed to sleep at many people's house and she can't sleep anywhere with post-pubescent males. That worked because I'm single and my son(16m) lived with his dad. I have him every summer and every other holiday and this year he was supposed to have this Christmas with his dad but his dad died unexpectedly. He died from a pulmonary embolism. So custody is obviously changing back me. He's with my ex MIL (who I do not like and was super abusive to my ex husband) and he's flying out to me tonight. My daughter is upset because her sleepover is ruined since her best friend can't be there and it's hard for her to have a good birthday when it's so close to Christmas. I spoke with the friends mom and she said while she's sorry that happened her boundaries are strict and I respected it. Now my daughter is upset and doesn't want the party at all.

Edit: Her best friend's mom doesn't have the space to host a sleepover. I told my daughter they could still do fun things during the day. Her friend would just have to go home at night and she didn't like that either

@Erika Lee My son doesn't have friends here. He mainly lived with his dad for like 10 years.