Brie Bella thinks her twin Nikki has ''more strength than any woman'' she knows.

The WWE superstar has admitted it's been really hard for her to sit back and watch her sister go through her heartbreaking split from John Cena, who she was dating for six years, but she knows the brunette beauty will get through it and come out stronger because she's ''fearless.''

Speaking to PEOPLE.com, Brie, 34, said: ''She's good, they call her fearless Nikki for a reason. She always puts on that brave face. My sister has more strength than any other woman I know, especially Wonder Woman. She's bigger than that.''

Nikki and John - who were due to get married next month after getting engaged last year - filmed the trials and tribulations of their relationship for their E! show 'Total Bellas' and Brie has admitted it was really tough for her to watch because she wants to ''protect'' her sister.

She explained: ''I really had to take a step back and allow it and that was really hard on me because it's my twin. I want to protect her from everything. This has been the hardest season to film for me because all I want to do is protect her and keep everyone away, but this is what we do. I have to give a lot of credit to John and Nicole. They really opened up their lives and they really wanted to close the curtain and be like this is it, we're done. My sister is really great with her fans in a way where she lets them connect with her. She lets them like go, 'My life isn't perfect and isn't easy' and lets them see the playbook of her life.

''John and Nicole allow the fans to see some very personal conversations, that to be honest, I was mind blown about. [Husband] Brian and I both said, 'I don't think we'd allow them to see those conversations' but they do. I give them a lot of credit.''

John and Nikki announced their shock split on her Instagram account last week.

It read: ''While this decision was a difficult one, we continue to have a great deal of love and respect for one another. We ask that you respect our privacy during this time in our lives.''