Here is my comment:

lol. why takes a lot of courage? usually you don't need to ask anything. just need to tell them your budget. hahaha... anyway, do read up the basics such as the 4Cs:

Go to Audrey's to do some price survey.
Learn about diamonds:
Prosumer Diamonds
Beyond4cs
Niceice

secondly, don't rush into buying anything. please don't feel that you are obliged to buy from the salesperson even if he/she is very nice to you, think it through.

thirdly, do share with us the diamond details you are looking at.

Here is my answer for your questions:
1. If not mistaken, proposal ring is the same as engagement ring. This is the ring you used during proposal, when you kneel down and pop the question. The ring that you exchange during wedding ceremony is wedding band, which is another different ring. There is actually one more ring before engagement ring, which is called promise ring, but seldom hear people talk about it these days. As far as I am concerned, I have only one engagement ring and one wedding band for my wife.

2. Most jewellers will give you free resize for 1 time. Just ask and see what they tell you.

3. In Malaysia, you can try iDo Jewellery or Tailored Jewel.

4. Love & Co price is negotiable. It is still a typical jewellery store. Its sister company is actually SK Jewellery from Singapore. You let us know the specs and price, and I am sure some of us will give you our opinions.

Good luck in your diamond hunting! 

Of course you will be getting the engagement ring first! 

It is not about carat, it is your sincerity that counts, hahaha.... Anyway, you should be able to get at least a 0.3ct, which actually is not that small. With your budget, you can consider the following:

1. Tailored Jewel is running promotion: https://www.facebook.com/tailoredjewel/phot...?type=3&theater (Money-back if unsatisfy!)
2. ZCOVA is running promotion: https://www.facebook.com/zcovajewels/photos...?type=3&theater

However, since you mentioned that your girlfriend likes Love & Co. You should pay them a visit. My friend managed to get his engagement ring below RM 5K. Not sure about the specs though. One thing good about Love & Co is that their ring setting is very nice (based on my experience with SK Jewellery).

And yes, wedding band in general is cheaper than the engagement ring.

The price is definitely marked-up due to rental, salary, and commission. Comparing to Tailored Jewel, Tailored Jewel is selling 0.25ct E VS2 + 18K white gold setting @ RM 3,300. Higher colour but cheaper price (Not sure comes with GIA cert or not though because the size is below 0.3ct, if you are interested, you can check with Tailored Jewel.) Alternatively, if you are focusing on ring design, you can look for iDo Jewellery at Bukit Jalil (Contact her via Facebook for appointment.)

For that diamond offered to you at Love & Co, which laboratory graded the diamond? Is it IGI? Or some other lab?

I think the main benefit of Love & Co is the ring design. They really look nice. Do they do resize? Or do they exchange with another setting if ring size not correct? 

Free resize hmm? Are their ring settings made in belgium? Or locally?