kanozyo ha simekiri wo tyanto mamoru.

は marks the topic, so 彼女は means as for her. It frames what follows as a comment about her general tendency or the current discussion topic.
Use が when you want to mark or emphasize the subject (often answering who).

• 彼女は締め切りをちゃんと守る。 As for her, she meets deadlines properly. (neutral, descriptive)
• 彼女が締め切りをちゃんと守る。 It is she who meets deadlines properly. (contrastive or answering 誰が…？ who does…?)

Typical Q-A:

• 誰が締め切りを守るの？ — 彼女が守る。 (Who meets the deadline? — She does.)

守る is a transitive verb that takes a direct object, so the thing you keep/observe is marked with を: 締め切りを守る.

• に is wrong here; use に with different verbs like 間に合う (be in time): 締め切りに間に合う.
• Dropping を can happen in very casual speech, but it’s safer and more natural to keep it: 締め切りをちゃんと守る.

With 締め切り, 守る means to keep/observe/adhere to a deadline. Other common collocations:

• 約束を守る keep a promise
• 規則・ルールを守る follow rules
• 時間を守る be punctual
• 秘密を守る keep a secret

The opposite is often 破る (break/violate): 締め切りを破る, 約束を破る.

ちゃんと is a manner adverb meaning properly, reliably, as expected. It emphasizes doing something the right way.

• きちんと is a bit more formal/neater in tone than ちゃんと and is safe in writing: きちんと守る.
• しっかり adds a sense of firmly/solidly; with 守る, it can imply strictness or thoroughness: しっかり守る.
• 必ず means without fail/certainly; it stresses certainty, not manner: 必ず締め切りを守る.

In formal business writing, prefer きちんと, 必ず, or set phrases like 厳守.

Yes. ちゃんと is a sentence adverb and can float within the predicate:

• 彼女は締め切りをちゃんと守る。 (neutral)
• 彼女はちゃんと締め切りを守る。 (slightly earlier emphasis on the manner)
• With the subject omitted: ちゃんと締め切りを守る。 (common)

Avoid 締め切りを守るちゃんと (unnatural). Also, don’t say ちゃんとに; ちゃんと is already an adverb.

Plain nonpast in Japanese covers:

• Habitual/generic: she tends to do it.
• Future: she will do it (context decides).

To clarify:

• Habitual: 彼女はいつも締め切りをちゃんと守る。 (always)
• Future specific: 彼女は今回の締め切りを守る。 (this time)

The progressive 〜ている can mark habit when supported by context/frequency words:

• 彼女は（いつも）締め切りを守っている。 (she habitually meets deadlines) Without such cues, 守っている may be read as currently complying with a specific deadline.

彼女 can mean she or girlfriend. In everyday conversation, third-person pronouns are often avoided; people prefer names or just omit the subject when understood.

• Natural: （田中さんは）締め切りをちゃんと守る。
• Using 彼女 is fine in writing or when there’s no risk of confusion, but in casual talk 彼女 often implies girlfriend.

Use the potential form of 守る:

• 彼女は締め切りをちゃんと守れる。 (She can meet deadlines properly.)

With potential verbs, the object may be marked by が in formal grammar, but を is very common in modern usage:

• 締め切りが守れる (also possible) vs 締め切りを守れる (very common).

You can also use 間に合う:

• 彼女は締め切りに間に合える is uncommon; instead say 彼女はいつも締め切りに間に合う (as a habitual statement).

Insert a frequency adverb near the verb:

• 彼女はいつも締め切りをちゃんと守る。 always
• 彼女はたいてい締め切りを守る。 usually
• 彼女はめったに締め切りを守らない。 rarely (note the negative)
• 彼女は絶対に／必ず締め切りを守る。 without fail