tā liáng le tǐwēn yǐhòu, cái zhīdào zìjǐ fāshāo le.

Because 量 has more than one pronunciation.

• liáng is usually the verb to measure
• liàng is often a noun meaning amount, quantity, capacity

In 量体温, 量 is a verb, so it is read liáng.

Examples:

• 量体温 = take/measure someone’s temperature
• 雨量 = rainfall amount
• 数量 = quantity

Yes. It is a very normal Mandarin verb-object phrase:

• 量 = measure
• 体温 = body temperature

So 量体温 literally means measure body temperature, and in natural English it is usually take someone’s temperature.

You can also expand it:

• 给她量体温 = take her temperature
• 医生给我量了体温 = the doctor took my temperature

The first 了 is the perfective aspect marker. It shows that the action of taking the temperature was completed.

So:

• 量了体温以后 = after taking her temperature

It does not simply mean past tense. It marks the action as completed before the next thing happened.

This is important because the sentence describes a sequence:

1. she took her temperature
2. only then did she find out she had a fever

Because in a verb + object phrase, the perfective 了 often goes right after the verb:

• 量了体温
• 吃了饭
• 看了医生

This is the normal way to mark the action as completed.

If 了 comes at the end of a clause, it is often a different kind of 了 that marks a new situation or change of state. In this sentence, the first 了 is clearly the verb-related perfective marker.

The second 了 is different from the first one.

In 自己发烧了, this 了 marks a new situation or change of state: she has come down with a fever, or she now realizes that this condition is true.

So the two 了 do different jobs:

• 量了体温: completed action
• 发烧了: new state / change of condition

This is a very common pattern in Mandarin:

• 我饿了 = I’m hungry now / I’ve become hungry
• 他病了 = he has fallen ill
• 天冷了 = the weather has turned cold

以后 means after, and it follows the event that happens first.

So:

• 量了体温以后 = after taking her temperature

Chinese often puts words like 以后, 之前, 的时候 after the action or clause they relate to.

Compare:

• 吃饭以后 = after eating
• 下课以后 = after class ends
• 看完医生以后 = after seeing the doctor

So the structure is:

[first action] + 以后, [main clause]

Not exactly. 才 means something like:

• only then
• not until then
• only after that

It adds the idea that the realization happened late, or only after the temperature was taken.

So:

• 她量了体温以后，才知道自己发烧了。

means more than simple sequence. It suggests:

• before taking her temperature, she did not know
• taking the temperature was what finally made her know

If you removed 才, the sentence would sound more neutral and just describe order. With 才, there is stronger emphasis on only after that.

That is a very common question. In Mandarin, 知道 can mean not only know, but also come to know or find out, depending on context.

Here, because of 才, the meaning is naturally:

• only then did she know
• only then did she realize
• only then did she find out

So 才知道 is a very common everyday pattern.

Other words are also possible, but with different nuance:

• 发现 = discover
• 意识到 = realize, become consciously aware of

But 才知道 is very natural and common in speech.

自己 means oneself / self / herself / himself, depending on context.

Here it refers back to the subject 她, so:

• 自己发烧了 = that she herself had a fever

In this sentence, there is no real ambiguity, so 自己 naturally refers to 她.

You could also say 她自己, but that usually adds emphasis:

• 她才知道她自己发烧了

That sounds a bit more emphatic than necessary here. Plain 自己 is the normal choice.

In Mandarin, 发烧 is usually treated as a verb meaning to have a fever.

So you can say:

• 我发烧了 = I have a fever
• 她没发烧 = she doesn’t have a fever
• 孩子在发烧 = the child has a fever / is running a fever

This is one reason Mandarin illness expressions can feel different from English. English often uses have + noun:

• have a fever
• have a cold

Mandarin often uses a single verb:

• 发烧 = have a fever
• 感冒 = catch/have a cold

No. In Chinese, if the same subject continues, it is very common to mention it once and leave it understood afterward.

So:

• 她量了体温以后，才知道自己发烧了。

is perfectly normal.

The implied subject of 才知道 is still 她.

You could say:

• 她量了体温以后，她才知道自己发烧了。

But that extra 她 is usually unnecessary unless you want special emphasis or contrast.

Yes. That is also very natural.

Both of these are fine:

• 她量了体温以后，才知道自己发烧了。
• 量了体温以后，她才知道自己发烧了。

The difference is mainly in what comes first in the sentence:

• starting with 她 foregrounds the person
• starting with 量了体温以后 foregrounds the time/sequence

Both are standard Mandarin.

Yes, it often can.

You can say:

• 她量了体温，才知道自己发烧了。

This is also natural and still clearly means that taking the temperature happened before the realization.

Adding 以后 makes the sequence more explicit:

• after taking her temperature, only then did she know...

Without 以后, the sentence is a little more compact, but the meaning is basically the same in this context.