The planner does not perform any calculations according to DIN 276

So yes, if service phase 8 is commissioned, the cost determination must also take place – it is also paid for by the client (or at least the architect wants to get the money – regardless of what she actually delivered).

How far this then goes I don’t know / however, my only approach against this woman is precisely to demand the services, since she is already requesting the final invoice – and with payment of this, the architectural services would also be accepted.

And since I obviously don’t think enough like a lawyer, because I still don’t understand what use the document has (other than that you should pay for its creation), my opinion remains to hire a lawyer.

I didn't build with an architect, so I am completely unfamiliar with the HOAI.

The first thing I noticed is that when I add up the percentage figures in the contract, I get 87%. So not all service phases have been agreed upon?

Furthermore, it would probably be necessary to check which version of DIN 276 is applicable at all. The contract is certainly already several years old. Search for: "Do costs have to be determined immediately according to the new DIN 276?"

As far as I understand, there are major differences between the old and new DIN 276. If the old one still has to be applied, the cost estimate in service phase 2 must be made according to DIN 276 (which presumably happened according to #7). For the determination of the billable costs, this could also be applied, but apparently, contrary to what is stated in the contract, the billable costs were determined according to the Winden construction table, i.e., not based on the actual costs.

And again about the cost explosion, your father received, as you claimed, a cost estimate per individual trades with minimum and maximum. If the bricklayer's offer is so much more expensive than the maximum estimated there, one could have intervened back then and pulled the emergency brake. It has been through all the media that construction prices are exploding and craftsmen write defensive offers. If now, after 4 years, the daughter (who is not a contracting party) comes in with a loud indication and questions everything from the last 4 years that was previously approved and signed by the contracting party, I would let her be dismissed.

If necessary, also with the blanket statement that this DIN is unknown to her.

(At the latest) with the payment for services which she 2. should not have provided and 1. did not provide, an administrative offense and a criminal offense have been realized, not least.

A lawyer would not understand what the OP still intends to do with the now completely useless calculation. It is a basic service (as said, = obligation and not optional, theoretically waivable but not unilaterally). The architect did not provide it and her statements about it can be offered as evidence to a court. Whether a complaint about it is still appropriate after four years, I do not know – but I suspect yes, since the deadline probably only starts with the final invoice. When the OP will finally seek legal advice, only the gods know. The determination of whether the architect actually is one is easy to make and has already been described here. I must now say goodbye here (although I just came back from shopping, but forgot the popcorn). A tug-of-war about this calculation would probably be seen by the magistrate Wunder as contempt of court. Kindergarten.

she is not one. Allegedly she is a graduate engineer and now officially calls herself only a specialist planner

she is not one. Allegedly she has a diploma in engineering and officially only calls herself a specialist planner

But with her there is a contract for work or similar, in which she acts as "architect"?

Yes, she has a planner contract for the Alp 1-9