Never thought my relationship with my sister could be so hurtful. Anyone else experience this?

I (32F) and my sister (35F) were never really close when we were young kids, however our teen years and early adulthood changed that and we became best friends then. We're extremely different personalities (chalk and cheese!) but still used to get along so well.

We also have very different lives - I've been single most of my life (was recently in a relationship but not anymore) and now pursuing a PhD in art and she got married at 27, is a successful lawyer and has two beautiful boys who I love more than life!

Recently, in the last two years or so (since her second baby), our relationship has changed drastically. She no longer has time for me or my life and is swamped with work, her kids and husband. It’s extremely overwhelming for her so of course I understand this and I’m always helping and supporting her where I can. But she's never interested in my life or struggles or offers the kind of support I need, yet I'm always there for her and her kids.

I think she looks at my life with a bit of envy because she’ll occasionally make remarks like "at least you get to go home and relax because you don't have kids, I don't know when was the last time I watched tv". I laugh it off but also try to explain to her the difficulties of going through life completely alone. I guess we just don't understand each other anymore.

There’s always a lingering tension between us now. My mom doesn't want to get involved and says we should sort it out between us. I just don't know how. It's come to a point where I'm so hurt by the things she says to me and realising I’m slowly losing my best friend and I don't think she realises how much our relationship is actually changing. When I bring it up, she says I’m too sensitive or gets angry, emotional and very defensive.

I’m just so tired of always having to be the bigger person to keep the peace. My mom always says “her life is so hectic, you should just apologise to her and move on”. I always wonder if I would be treated this way and asked to do this if I had a husband and family of my own.

I guess this is more of a vent. I don’t know how to remedy this and fear it’s the beginning of an estranged relationship. I keep thinking of the lyric by Taylor Swift; “if I can’t relate to you anymore, then who am I related to?”

Anyone else been through this? Please share some advice / words of wisdom.