Would it be rude to decline a neighbor's invitation to visit an onsen together?

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Hi everyone,

I'm a 48-year-old woman from Pakistan and I've been living in Japan for about a year because of my husband's job.

I've been fortunate to have a very kind and friendly neighbor around my age. She's helped me with a lot of little things since I arrived, and recently she invited me to go to an onsen with her and a few of her friends next week.She reassured me that the atmosphere at an onsen is very peaceful, that nobody stares at anyone else, and that I would probably feel comfortable within 10–15 minutes.

I've never been to an onsen before, so I'm feeling a bit unsure. Part of me is curious to try it, but I'm also nervous about the experience .

I was hoping to get some perspective from Japanese people:

1. Is it common for neighbors, especially women of my age to go to an onsen together?

2. If I politely decline the invitation, would that be considered rude or unfriendly?

I genuinely appreciate her kindness and don't want to accidentally offend her or damage our good relationship.

Thank you for any insights or advice!