Learn English – use “that I like” in the following sentence

I would probably use 'would' in a sentence like that if I was discussing something that might or might not happen:

If she goes, it seems as though she would be so far separated from us.

On the other hand, I would be more likely to use the author's construction if it was something that was definitely going to happen, and I was talking about what I thought the result would be:

When she goes, it seems as though she will be so far separated from us.

The use of 'will' indicates that the event is certain to happen, while the weaker 'it seems as though' indicate that the results of that event are subjective and/or uncertain.

It's also worth noting that 'will' does not have to imply a strong certainty. It indicates that the speaker/author has no reason to signal uncertainty, but it's a default option as much as a positive signal. If a positive indication of certainty is needed, most people will add an extra modifier such as 'will definitely' or 'will obviously'.

Your sentence is fine and polite as written. I have no grammatical suggestions.

However there may be more diplomatic ways to tell customers that you have included extra charges in the past, but not actually told them about it. This depends entirely on the context.

The general term is charge for costs associated with an item or service. You can charge a customer for the item itself or the service itself, and also charge them additional costs associated with other related expenses.

If you are a company that sends products to people through the mail, then shipping (the cost to send the product) is an expected cost. Sometimes this is referred to as shipping and handling, abbreviated as S&H. It's not uncommon to state the total price for an item, including shipping and handling.

A fee is usually the cost associated with a service of some kind, for example a registration fee, a processing fee, a licensing fee, and so on. Fees may also be penalties for some situation, such as a late fee or a returned check fee. There may be fees associated with the cost of delivering a product, if the delivery requires some kind of special service (an installation fee, for example).

A general way to talk about a document that details the charges in the bill is an itemized bill, or more formally a bill of sale. Less formally you can talk about an itemized receipt, or a breakdown of costs.

So, again as a suggestion:

In the past we included shipping in the total cost of the item, but we have decided to provide an itemized receipt to our customers so they can see a detailed breakdown of the charges.