Cold Rent Increase (NOT Nebenkosten increase as far as I understand)- Legal?

Hey all,

I just got a notice from my landlady:

"First of all, I would like to thank you very much for the reliable and trusting rental relationship over almost 2 years. I hope you are comfortable in your home.

Due to the increase in the rent index and the ancillary costs, an adjustment of the rent is unavoidable. Therefore, I would like to announce a cold rent increase of 80 euros, i.e. from 1200 euros to 1280 euros, as well as the ancillary costs from 125 euros to 150 euros, so that the total rent is 1430 euros, as of March 1st, 2023. Please adjust your payments accordingly."

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I know no one is a lawyer here and your answers/advice can't be 100% without seeing my lease contract, however, my concern is this:

- Is it (in general) legal for my landlord to increase rent for the reasons she gave (rent index and ancillary costs)? I pay all of my utilities separately and care for the garden and property areas.

- She already charged me for a raise in "ancillary costs" a little over a year ago, and increased my rent after that by 25eur per month to cover those said "rising ancillary costs". Is it legal for her to raise my rent AGAIN for this same reason?

- I'm from the US, the way things work there is that once I sign my lease, my rent payment is my rent payment- they are not allowed to increase my rent until I renew my lease... If their costs increase during my leasing period, that's considered "their problem" and they just have to eat it until I renew or they rent to someone new. Is it really acceptable in Germany for landlords to increase rent in the middle of your contract, when you're essentially trapped just because their own expenses have increased?

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For additional context: My landlady breaks down my total rent into "rent" and "ancillary costs"- however, she does not pay any of my utilities (water, heat, electricity, internet, etc are paid by me separately). Her "ancillary costs" are listed in my contract as:

- Trash pickup

- Sewage

- Chimney cleaner (once a year)

- Insurance

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I don't want to start problems with my landlady but a 105eur increase per month is a lot when she already had increased my rent semi- recently... I'm scared to start shit with her, as finding a new place to live would take more than 3 months + all of the moving costs involved would kill me financially right now. However, I don't want to agree to a potentially illegal price increase/ let her bully me...

Or more importantly, I'm concerned that until my lease is done (2 more years, 4 year lease in total), that my rent will continue to increase randomly and that I can be priced out of my home at any moment just because...

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TLDR: Can a landlord increase your cold rent, due to a claim of an increase in rent index and the ancillary costs? Is that my problem if her "ancillary costs" are NOT utilities?