I found out last year that I have a half sister. She is 5 years younger than me and was conceived when my parents split for a year. My mum had no clue that she existed either. My dad sat us down and told us all about her about 18 months ago. There was a lot of drama which was to be expected but my mum decided to stick by him as they were filing for divorce before they reconciled. For context I also have an older sister who is 28, I am 23 and my youngest sister is 18. My dad knew that there was a chance she was his but in his words 'he wasn't sure until he saw her'. She is his spitting image, quite literally the female version of him.
My dad's side of the family are thrilled that she is his and have welcomed her with open arms. My mum's family were shocked but equally have been very welcoming and have treated her the same as they would us e.g. buying her a lovely makeup set for her birthday, including her in the family trip to Center Parcs. However, she has since told my dad that she doesn't want to do anything with my mum's family as she thinks it's 'weird', so my dad will be staying at home with her on Boxing Day instead of going to our Gran's as we have done every year.
Since he told us about her we have seen her quite frequently and she now lives with my mum and dad about half of the time. My mum has done her best to involve her and ensure that she gets to spend time with her dad but not feel as though she is a spare part, if you see what I mean? My dad feels guilty as he never paid child support or was involved with her growing up. This was not entirely his fault as her mother insisted that her ex-partner was the father and refused any sort of DNA testing, my dad didn't want to rock the apple cart so let them get on with it. My Dad has since paid for all of her driving lessons, bought her a car and paid for the insurance, he buys her clothes, phones, iPads etc. and pretty much anything she wants as he feels guilty for not 'stepping up' for her.
I have recently had a baby so decided to invite my sister round to meet her niece along with my eldest sister, we haven't spent much alone time together as she gets very shy around myself and our sister and tends to just go on her phone. I sent her a picture on Watsapp accompanied with a text that said 'Hi, Daughters Name can't wait to see her Auntie! We would love to see you, we are free any day this week. Just let me know x'
She is now driving and only goes to college a few days a week, I live about a 5 minute drive from the college so thought it might be nice for her to pop in. I hadn't heard back from her in a few days so assumed she was busy at college/work. I then got a very nasty message from my Dad that read 'I am disappointed in you, your sister was very much looking forward to seeing the baby. She has been in tears and does not feel like a part of the family. You and DSis1 should be ashamed of yourselves, alienating your sister this way. Disgusting behaviour.' My DSis1 went bonkers and showed my Dad the text in which I invited Dsis2 over however, my dad is standing firm and says that this is not the first instance of us alienating his 'little girl'. My mum is furious, particularly as my dad is no longer talking to myself or my sister and will not even be in the same room as my daughter who is his first GC.
I'm not sure what to do? I know that to apologise and grovel would be the easiest option but myself and my sister do not feel we have done anything wrong... Any advice?